Some standard content:
National Mongolian Standard of the People's Republic of China
Measuring methods for broadcast video tape
Measuring methods for broudcast video tape1 Subject content and scope of application
This standard specifies the test methods for broadcast video tapes. This standard applies to video tapes with a width of 25.4mm and 19.00mm. 2 Reference standards
GB 1779.16.30mm Broadcast audio tape performance test method GB3660 Unified weighting network for measuring continuous random noise of video cheeks 3 Explanation of terms
3.1 Reference tape, a standard tape used to measure the electromagnetic characteristics of the tape under test. 3.2RF output: The output voltage of an FM carrier with a 100% white level signal during playback. GB/T 14854.1—93
3.3 Maximum video current of the reference tape: The video current when a 50% white level FM signal is recorded on the reference tape and the maximum RF output is obtained during playback.
3.4 Specified bias: The bias current at which the maximum output is obtained when a 1kHz sine wave signal is recorded on a reference tape and played back. 3.5 Specified input level: The input signal level of the test VTR when a 1kHz sine wave signal is recorded on a reference tape with a specified bias current and played back to obtain a specified output level. This standard stipulates that the magnetic flux recorded on the tape is 100nWb/m as the specified input level. 3.6 Specified output level: The output signal level obtained when the specified input signal level is played back on the test VTR. 3.7 Reference value: The electromagnetic conversion characteristic value obtained on the reference tape. 3.8 Visual weighting network: A network that compensates for frequency characteristics by taking into account the relationship between visual characteristics and noise. 3.9 Auditory weighting network: A network that compensates for frequency characteristics by taking into account the relationship between auditory characteristics and noise. 4 Measurement conditions
4.1 Standard measurement conditions: temperature 20±1°C, relative humidity 40%~52%; in addition, temperature 5~35°C, relative humidity 40%~80% is also considered as standard test conditions. 4.2 Sample pretreatment: The sample must be placed in the standard measurement condition for more than 24 hours before testing. 5 Measuring instruments and video recorders for measurement
5.1 Measuring instruments and their requirements are shown in Table 1. Approved by the State Bureau of Technical Supervision on December 30, 1993, and implemented on September 1, 1994.
Name of device only
Low frequency signal generator
Low frequency filter
Band pass filter
High pass filter
Variable resistance attenuator
Level meter
Distortion meter
OscilloscopebzxZ.net
Auditory weighting network
Regular auditory weighting network
Video signal generator
Impurity measuring instrument
GB/T 14854.1- 93
Frequency range: 20Hz20kHz
Output level: Maximum +20dBm (distortion below 0.1%)Cut-off frequency: 500kHz
Input, output impedance: 75
Maximum allowable power: 1W
Center frequency, 1kHz
Bandwidth: 100Hz Below
Input and output impedance: 6000
Maximum allowable power: 1W
Cut-off frequency: 10kHz, 100kHz
Input and output impedance 750
Maximum allowable power: 1W
Adjustable range, 0~91dB or more (measurement scale 0.1dB)Input and output impedance: balanced, H type, 600mMaximum allowable power: 1W
Measuring range: -80~~+20dRm
Frequency range: 20Hz~20kHz
Input impedance: 6 000m, 10km
Trace range: 30~~0,1% or less
Pre-rate range t50Hz～15kHz
Input impedance, 600m, 10km
Vertical rate range DC～15MHz or more
Inflammation sensitivity: 5mV～20V/bin
Horizontal frequency range: TX~2MHz or more
Scanning speed; 0.Jμ8～1.55/bin
Correction voltage: 0.05~100V
Input and output impedance: Balanced 6000| |tt||Auditory compensation characteristics: Conform to A-weighted characteristics
Input and output impedance: 75m
Visual compensation characteristics: Conform to GB3660
Signal: Test video signal with TV synchronization signal (Figure 4 and Figure 5) Output: 750,0~1,1Vr-5
Frequency range: 40Hz~10MHz (±0.2dB)Input signal: Regulatory signal or image signalSerial number
Instrument name
Clutter measuring instrument
Level recorder
Surface resistance measuring instrument||tt ||GB/T-14854.1—93
Continued Table 1
Technical Specifications
Input Signal Level: 0～1V
Allowable Error of Voltage Indication, ±5% or Less Synchronous; Internal, External
Impedance: 750,IMQ, 30pF or Less
Clutter Measurement Range: 0.3~100mV(rm8)Sampling Signal S/N Ratio Measurement Range: 20～70dBRMS Detection: Square Law Detection
Frequency Range: DC~6MHz
Input Impedance: 750,10k Above
Recording speed, above 300mm/g
Indication; Effective value
Measurement range: 10°～10g and above
Addable voltage range, 100~600V
5.2 Test disk video recorder, normally used adjusted 25.4mm(1in) C format and 19.00mm(machine.
6 Measurement method
6.1 Measurement of tape geometric dimensions and mechanical properties 6.1.1 Bandwidth: Same as 4.1 in GB1779.1. 6.1.2 Tape thickness: Same as 4.2 in GB1779.1. 6.1.3 Tape length: measured with a timer equal to or higher than that on the test VTR 6.1.4 Residual elongation:
in) High-band Umatic video
During the test, the ambient temperature is 20~～30℃, and the relative humidity is 50%～80%. A section of tape about 1m long is first fixed on the residual elongation meter with a force of 0.05N. A force of 30N is added. After 3 minutes, there is still a force of 0.05N. After another 3 minutes, the residual elongation of the tape is measured 1
In the formula: - the increment of the sample length after the force of 0.05N is retained for 3 minutes; - the initial length of the sample.
6.1.5 Interlayer adhesion: Same as 4.5 in GB1779.1, except that the winding tension is changed to 30N (about 3k). 6.1.6 Transverse bending deformation: a 25cm long magnetic tape is placed on the reference plane with both sides facing downwards, and the highest point is measured. When the magnetic powder layer faces downwards, it is (+) and when the magnetic powder layer faces downwards, it is (-).
6.1.7 Longitudinal bending deformation: the same as 4.4.3 in GB 1779.1. 6.1.8 Surface resistance: as shown in Figure 1, the distance between the two electrodes of a 1/4 circular cross-section metal with a radius of about 1cm is L (mm), and the contact surface between the magnetic tape and the two electrodes is 90°. A 300g weight is hung on each side of the magnetic tape. A DC voltage of more than 100V and less than 600V is applied to the two electrodes, and then the DC current is measured. The magnetic powder layer is facing upwards and downwards, and the measurement is carried out separately. The surface resistance is calculated as follows: Surface resistance (MQ)
Where: V-
Voltage, V;
Current, μA:
Tape width, mm,
Distance between electrodes, mm.
(When W is equal to L)
Precautions during testing: After adding voltage, wait for the current value to stabilize before reading. Generally, if the voltage is less than 100V, the current value is too small and the error is large. If the voltage is higher than 600V, discharge will occur and the current value will be unstable. 6-2 Electromagnetic characteristics
The block diagram for measuring video characteristics is shown in Figure 2.
The block diagram for measuring recording characteristics is shown in Figure 3. The test signal waveform a is shown in Figure 4.
The test signal waveform b is shown in Figure 5.
According to the measured items, use the switch to connect the corresponding filter or measuring instrument. 6.2.1 Optimal video current ratio: Input signal waveform a, slowly increase the video current to record, then replay, use an oscilloscope to view the RF output, and measure the maximum,The video current at RF output, and then calculate the maximum video current ratio I according to the following formula, I (%)
Where: I--the video current at maximum RF output; the video current at maximum RF output on the reference band. Direct wash voltage
100
600YBT
Audio value signal generator
Regular sugar signal generator
Level meter
Recording part
The most sound national road
Partial tunnel loop
GB/T14854.1-93
Recording points
Recording summary
Image current
Recording system for use in the environment ||tt| |Playback section
Pendant circuit
Test video recorder
Figure 4 Test signal waveform a
Playback section "
RF box
The most daring to ask the way
Chain display
Clutter tester
Image source monitor
Bandpass filter
Audio weighting network
Effect display
Measuring instrument
GB/T 14854. 193
Figure 5 Test signal waveform b
L-brightness level, 157mV, B-color sync pulse level 300mVpVm-color subcarrier level, 664mYpVnt test level, 700mVmtS-step level 300mV6.2.2RF playback output sensitivity
Use signal waveform a and record it with reference video current I. Use an oscilloscope to observe the envelope average value of the playback RF output, and then calculate the RF playback output sensitivity SkF
Sere(dB)=20lg according to the following formula
Where: V——average value,
V reference value.
6.2.3 Replay RF output sensitivity non-uniformity Use signal waveform a, record with reference video current 1, use oscilloscope to observe the maximum and minimum values of the envelope of the replay RF output, and then calculate the replay RF output sensitivity non-uniformity according to the following formula SrNSrnN(dB)=20lg %
Where: B——maximum value 1
A——minimum value.
In addition, the data from the beginning of a video track to 500us or 500us before the end of the track within a field is not counted. 6.2.4 Image Brightness Signal Noise
Use signal waveform a to record with reference video current I, then replay it, pass through a 100kHz high-pass filter, and use a noise tester to measure the noise in the output signal. Perform the same test on the reference band, subtract the obtained reference value from the measured value of the tested band, and express it in dB. When performing this test, Use the unified weighting network specified in GB3660. 6.2.5 Image chrominance signal noise
Use signal waveform b, record with reference video current I and then replay. Through a 10kHz high-pass filter and a 500kHz low-pass filter, use a noise tester to measure the AM component and PM component in the replay output signal, and calculate the chrominance signal noise amplitude modulation component S/N (AM) and phase modulation component S/N (PM) according to the following formula. GB/T14854.1-93
VrpB)(dB)
S/N(AM)=20lg AM....
Vel(rp)_(dB)
S/N(PM)--20lg PM
Make the same measurement on the reference band, subtract the obtained reference value from the measured value of the measured band, and express it in dB. 6.2.6 Dropout
Use signal waveform a to record with reference video current I, then replay. Within 1 minute, the number of drops above 16dB shall be measured with dropout counter. 6.2.7 Freeze characteristic
H(6.4μs) and drop
Use signal waveform to record, replay it in freeze state, record the replayed RF output level with recorder, and measure the time when the signal level drops to half of the original level.
6.2.8 Sound working bias
Use level 10dB lower than the specified input level to record 1kIIz sine wave, slowly increase bias current to record, in the replay path, find the maximum output bias current, and calculate the sound working bias IA-A×100
In the formula: A—Bias current at the minimum input level; A. \--Bias current at the maximum output of reference band. The bias current at the maximum output level is obtained according to Figure 6. 0.5dB
Bias power supply
6.2.9 Sound sensitivity
Record the tape with a specified input level and a 1kHz sine wave signal under working bias, and use a level meter to measure the playback output level. Subtract the output level of the reference tape under the same conditions and express it in dB. 6.2.10 Sound sensitivity non-uniformity
Record the tape with a specified input level and a 1kHz sine wave signal under working bias, observe the output level, and find the maximum and minimum values. The difference between the two is expressed in dB. 6.2.11 Sound frequency characteristics
Record the tape with a 1kHz and 10kHz sine wave signal at 10dB lower than the specified input level, respectively, under bias, and then replay it. Use a level meter to measure their re-excitation output levels and find the deviation relative to the 1kHz output level. GB/T 14854. 1-93
The same measurement is carried out on the reference tape, and the playback deviation is also calculated. The sound frequency characteristic FF (dB) = BB is calculated according to the following formula.
Where: B——playback output deviation when testing on the measured tape; B. Playback output deviation when testing on the reference tape. 6.2.12 Sound distortion
Record a 1kHz sine wave signal at a level 6dB higher than the specified input level, and then replay it. Measure the third harmonic and express it as a percentage relative to the original signal.
6.2.13 Sound signal-to-noise ratio
Record the sound with a specified input level and a 1kHz sine wave signal under working bias magnetization. Measure the playback output level of this signal and the playback output level through the auditory compensation network when there is no signal, and calculate the signal-to-noise ratio (S/N) using the following formula: (S/N), (dB) = AB
Where: A——playback output level when there is a signal (dB) B——playback output level when there is no signal (dB). The characteristics of the auditory compensation network should meet the A-weighted characteristics. 6.2.14 Copy effect
Use a level 6d13 higher than the specified input level, and record a 1kHz sine wave signal. Record once every 10 figures or so. The length of each record is about 1/3 to 1/2 of a circle. Do not rewind before playback. After placing it in the test environment for 48 hours, rewind the tape and play it through a 1kHz bandpass filter. Use a level recorder to record only the output level (recording pen speed 300mm/s), and read the difference between the signal level and the copy level from the recording paper.
6.2.15 Demagnetization rate
Use a 1kHz sine wave signal 10dB higher than the specified input level to record under working bias magnetization, place it in the test environment for 48h, and measure the playback output level and the output level after demagnetization and passing through a 1kHz bandpass filter and then replaying it. D.(dH)-AB
In the formula, D.—demagnetization rate;
, A——playback output level after 48h B——playback output level after demagnetization.
Demagnetization current: On the reference band, use a level 10dB higher than the specified input level, record with a 1kHz sine wave, and then directly demagnetize.
Replay this signal, measure the playback output level after passing through a 1kHz bandpass filter, and get the current when 65dB is eliminated, and then increase it by 20% as the demagnetization current.
Additional Notes:
This standard was proposed by the Ministry of Radio, Film and Television. This standard was drafted by the Standardization Planning Institute of the Ministry of Radio, Film and Television. The main drafter of this standard was Chen Chengquan.193
Figure 5 Test signal waveform b
L-brightness level, 157mV, B-color synchronization pulse level 300mVpVm-color subcarrier level, 664mYpVntTest level, 700mVmtS-step level 300mV6.2.2RF playback output sensitivity
Use signal waveform a and record it with reference recording current I. Use an oscilloscope to observe the envelope average value of the playback RF output, and then calculate the RF playback output sensitivity SkF
Sere(dB)=20lg
Where: V——average value,
Vreference value.
6.2.3 Replay RF output sensitivity non-uniformity Use signal waveform a to record with reference video current 1, use an oscilloscope to observe the maximum and minimum values of the envelope of the replay RF output, and then calculate the replay RF output sensitivity non-uniformity SrNSrnN (dB) = 20lg %
Where: B——maximum value 1
A——minimum value.
In addition, the data from the beginning of a video track to 500us or 500us before the end of the track in a field is not calculated. 6.2.4 Image brightness signal noise
Use signal waveform a to record with reference video current I, then replay, pass through a 100kHz high-pass filter, and use a noise tester to measure the noise in the output signal. Perform the same test on the reference band, subtract the obtained reference value from the measured value of the tested band, and express it in dB. When performing this test, use the unified weighting network specified in GB3660. 6.2.5 Image chrominance signal noise
Use signal waveform b, record with reference video current I and then replay. Use noise tester to measure AM and PM components in the replay output signal through 10kHz high-pass filter and 500kHz low-pass filter, and calculate the amplitude modulation component S/N(AM) and phase modulation component S/N(PM) of chrominance signal noise according to the following formula. GB/T14854.1-93
VrpB)(dB)
S/N(AM)=20lg AM....
Vel(rp)_(dB)
S/N(PM)--20lg PM
Perform the same measurement on the reference band, subtract the obtained reference value from the measured value of the measured band, and express it in dB. 6.2.6 Dropout
Use signal waveform a to record with reference video current I, then replay. Within 1 minute, the number of drops above 16dB shall be measured with dropout counter. 6.2.7 Freeze characteristic
H(6.4μs) and drop
Use signal waveform to record, replay it in freeze state, record the replayed RF output level with recorder, and measure the time when the signal level drops to half of the original level.
6.2.8 Sound working bias
Use level 10dB lower than the specified input level to record 1kIIz sine wave, slowly increase bias current to record, in the replay path, find the maximum output bias current, and calculate the sound working bias IA-A×100
In the formula: A—Bias current at the minimum input level; A. \--Bias current at the maximum output of reference band. The bias current at the maximum output level is obtained according to Figure 6. 0.5dB
Bias power supply
6.2.9 Sound sensitivity
Record the tape with a specified input level and a 1kHz sine wave signal under working bias, and use a level meter to measure the playback output level. Subtract the output level of the reference tape under the same conditions and express it in dB. 6.2.10 Sound sensitivity non-uniformity
Record the tape with a specified input level and a 1kHz sine wave signal under working bias, observe the output level, and find the maximum and minimum values. The difference between the two is expressed in dB. 6.2.11 Sound frequency characteristics
Record the tape with a 1kHz and 10kHz sine wave signal at 10dB lower than the specified input level, respectively, under bias, and then replay it. Use a level meter to measure their re-excitation output levels and find the deviation relative to the 1kHz output level. GB/T 14854. 1-93
The same measurement is carried out on the reference tape, and the playback deviation is also calculated. The sound frequency characteristic FF (dB) = BB is calculated according to the following formula.
Where: B——playback output deviation when testing on the measured tape; B. Playback output deviation when testing on the reference tape. 6.2.12 Sound distortion
Record a 1kHz sine wave signal at a level 6dB higher than the specified input level, and then replay it. Measure the third harmonic and express it as a percentage relative to the original signal.
6.2.13 Sound signal-to-noise ratio
Record the sound with a specified input level and a 1kHz sine wave signal under working bias magnetization. Measure the playback output level of this signal and the playback output level through the auditory compensation network when there is no signal, and calculate the signal-to-noise ratio (S/N) using the following formula: (S/N), (dB) = AB
Where: A——playback output level when there is a signal (dB) B——playback output level when there is no signal (dB). The characteristics of the auditory compensation network should meet the A-weighted characteristics. 6.2.14 Copy effect
Use a level 6d13 higher than the specified input level, and record a 1kHz sine wave signal. Record once every 10 figures or so. The length of each record is about 1/3 to 1/2 of a circle. Do not rewind before playback. After placing it in the test environment for 48 hours, rewind the tape and play it through a 1kHz bandpass filter. Use a level recorder to record only the output level (recording pen speed 300mm/s), and read the difference between the signal level and the copy level from the recording paper.
6.2.15 Demagnetization rate
Use a 1kHz sine wave signal 10dB higher than the specified input level to record under working bias magnetization, place it in the test environment for 48h, and measure the playback output level and the output level after demagnetization and passing through a 1kHz bandpass filter and then replaying it. D.(dH)-AB
In the formula, D.—demagnetization rate;
, A——playback output level after 48h B——playback output level after demagnetization.
Demagnetization current: On the reference band, use a level 10dB higher than the specified input level and record with a 1kHz sine wave, and then directly demagnetize.
Replay this signal, measure the playback output level after passing through a 1kHz bandpass filter, and get the current when 65dB is eliminated, and then increase it by 20% as the demagnetization current.
Additional Notes:
This standard was proposed by the Ministry of Radio, Film and Television. This standard was drafted by the Standardization Planning Institute of the Ministry of Radio, Film and Television. The main drafter of this standard was Chen Chengquan.193
Figure 5 Test signal waveform b
L-brightness level, 157mV, B-color synchronization pulse level 300mVpVm-color subcarrier level, 664mYpVntTest level, 700mVmtS-step level 300mV6.2.2RF playback output sensitivity
Use signal waveform a and record it with reference recording current I. Use an oscilloscope to observe the envelope average value of the playback RF output, and then calculate the RF playback output sensitivity SkF
Sere(dB)=20lg
Where: V——average value,
Vreference value.
6.2.3 Replay RF output sensitivity non-uniformity Use signal waveform a to record with reference video current 1, use an oscilloscope to observe the maximum and minimum values of the envelope of the replay RF output, and then calculate the replay RF output sensitivity non-uniformity SrNSrnN (dB) = 20lg %
Where: B——maximum value 1
A——minimum value.
In addition, the data from the beginning of a video track to 500us or 500us before the end of the track in a field is not calculated. 6.2.4 Image brightness signal noise
Use signal waveform a to record with reference video current I, then replay, pass through a 100kHz high-pass filter, and use a noise tester to measure the noise in the output signal. Perform the same test on the reference band, subtract the obtained reference value from the measured value of the tested band, and express it in dB. When performing this test, use the unified weighting network specified in GB3660. 6.2.5 Image chrominance signal noise
Use signal waveform b, record with reference video current I and then replay. Use noise tester to measure AM and PM components in the replay output signal through 10kHz high-pass filter and 500kHz low-pass filter, and calculate the amplitude modulation component S/N(AM) and phase modulation component S/N(PM) of chrominance signal noise according to the following formula. GB/T14854.1-93
VrpB)(dB)
S/N(AM)=20lg AM....
Vel(rp)_(dB)
S/N(PM)--20lg PM
Perform the same measurement on the reference band, subtract the obtained reference value from the measured value of the measured band, and express it in dB. 6.2.6 Dropout
Use signal waveform a to record with reference video current I, then replay. Within 1 minute, the number of drops above 16dB shall be measured with dropout counter. 6.2.7 Freeze characteristic
H(6.4μs) and drop
Use signal waveform to record, replay it in freeze state, record the replayed RF output level with recorder, and measure the time when the signal level drops to half of the original level.
6.2.8 Sound working bias
Use level 10dB lower than the specified input level to record 1kIIz sine wave, slowly increase bias current to record, in the replay path, find the maximum output bias current, and calculate the sound working bias IA-A×100
In the formula: A—Bias current at the minimum input level; A. \--Bias current at the maximum output of reference band. The bias current at the maximum output level is obtained according to Figure 6. 0.5dB
Bias power supply
6.2.9 Sound sensitivity
Record the tape with a specified input level and a 1kHz sine wave signal under working bias, and use a level meter to measure the playback output level. Subtract the output level of the reference tape under the same conditions and express it in dB. 6.2.10 Sound sensitivity non-uniformity
Record the tape with a specified input level and a 1kHz sine wave signal under working bias, observe the output level, and find the maximum and minimum values. The difference between the two is expressed in dB. 6.2.11 Sound frequency characteristics
Record the tape with a 1kHz and 10kHz sine wave signal at 10dB lower than the specified input level, respectively, under bias, and then replay it. Use a level meter to measure their re-excitation output levels and find the deviation relative to the 1kHz output level. GB/T 14854. 1-93
The same measurement is carried out on the reference tape, and the playback deviation is also calculated. The sound frequency characteristic FF (dB) = BB is calculated according to the following formula.
Where: B——playback output deviation when testing on the measured tape; B. Playback output deviation when testing on the reference tape. 6.2.12 Sound distortion
Record a 1kHz sine wave signal at a level 6dB higher than the specified input level, and then replay it. Measure the third harmonic and express it as a percentage relative to the original signal.
6.2.13 Sound signal-to-noise ratio
Record the sound with a specified input level and a 1kHz sine wave signal under working bias magnetization. Measure the playback output level of this signal and the playback output level through the auditory compensation network when there is no signal, and calculate the signal-to-noise ratio (S/N) using the following formula: (S/N), (dB) = AB
Where: A——playback output level when there is a signal (dB) B——playback output level when there is no signal (dB). The characteristics of the auditory compensation network should meet the A-weighted characteristics. 6.2.14 Copy effect
Use a level 6d13 higher than the specified input level, and record a 1kHz sine wave signal. Record once every 10 figures or so. The length of each record is about 1/3 to 1/2 of a circle. Do not rewind before playback. After placing it in the test environment for 48 hours, rewind the tape and play it through a 1kHz bandpass filter. Use a level recorder to record only the output level (recording pen speed 300mm/s), and read the difference between the signal level and the copy level from the recording paper.
6.2.15 Demagnetization rate
Use a 1kHz sine wave signal 10dB higher than the specified input level to record under working bias magnetization, place it in the test environment for 48h, and measure the playback output level and the output level after demagnetization and passing through a 1kHz bandpass filter and then replaying it. D.(dH)-AB
In the formula, D.—demagnetization rate;
, A——playback output level after 48h B——playback output level after demagnetization.
Demagnetization current: On the reference band, use a level 10dB higher than the specified input level and record with a 1kHz sine wave, and then directly demagnetize.
Replay this signal, measure the playback output level after passing through a 1kHz bandpass filter, and get the current when 65dB is eliminated, and then increase it by 20% as the demagnetization current.
Additional Notes:
This standard was proposed by the Ministry of Radio, Film and Television. This standard was drafted by the Standardization Planning Institute of the Ministry of Radio, Film and Television. The main drafter of this standard was Chen Chengquan.1-93
VrpB)(dB)
S/N(AM)=20lg AM....
Vel(rp)_(dB)
S/N(PM)--20lg PM
Perform the same measurement on the reference band, subtract the obtained reference value from the measured value of the measured band, and express it in dB. 6.2.6 Dropout
Use the signal waveform a and record it with the reference video current I, then replay it. Within 1 minute, the number of drops above 16dB is measured with a dropout counter. 6.2.7 Freeze characteristic
H(6.4μs) and drop
Use the signal waveform to record it, replay it in the freeze state, record the replayed RF output level with a recorder, and measure the time when the signal level drops to half of the original level.
6.2.8 Sound working bias
Record a 1kHz sine wave at a level 10dB lower than the specified input level, and gradually increase the bias current to record. In the playback path, find the bias current with the maximum output, and calculate the sound working bias according to the following formula IA-A×100
Where: A—Bias current at the minimum input level; A. \--Bias current at the maximum output of the reference band. The bias current at the maximum output level is obtained according to Figure 6. 0.5dB
Bias power supply
6.2.9 Sound sensitivity
Record a 1kHz sine wave signal at the specified input level with working bias, and use a level meter to measure the playback output level, and subtract it from the output current of the reference band under the same conditions, expressed in dB. 6.2.10 Sound sensitivity non-uniformity
Record a 1kHz sine wave signal at the specified input voltage over the entire length of the tape under the working bias, observe the output level, find the maximum and minimum values, and express the difference in dB. 6.2.11 Sound frequency characteristics
Record a 1kHz and 10kHz sine wave signal at 10dB lower than the specified input level under the working bias, then replay them, measure their re-excitation output levels with a level meter, and find the deviation relative to the 1kHz output level. GB/T 14854. 1-93
Carry out the same measurement on the reference tape, and also find the playback deviation. Calculate the sound frequency characteristics according to the following formula: FF (dB) = BB.
Where: B——playback output deviation when testing on the tested tape; B. Playback output deviation when testing on the reference tape. 6.2.12 Sound distortion
Record a 1kHz sine wave signal at a level 6dB higher than the specified input level, and then replay it. Measure the third harmonic and express it as a percentage relative to the original signal.
6.2.13 Sound signal-to-noise ratio
Record the sound at the specified input level and 1kHz sine wave signal under working bias. Measure the playback output level of this signal and the playback output level through the auditory compensation network when there is no signal, and calculate the signal-to-noise ratio (S/N) using the following formula: (S/N), (dB) = AB
Where: A——playback output level when there is a signal (dB) B——playback output level when there is no signal (dB). The characteristics of the auditory compensation network should conform to the A-weighted characteristics. 6.2.14 Copy effect
Use a 1kHz sine wave signal with a level 6d13 higher than the specified input level to record, record once every 10 pictures or so, and the length of each record is about 1/3 to 1/2 of a circle. Do not return before replaying. After placing it in the test environment for 48 hours, rewind the tape and play it through a 1kHz bandpass filter. Use a level recorder to record only the output level (recording pen speed 300mm/s), and read the difference between the signal level and the copy level from the recording paper.
6.2.15 Demagnetization rate
Use a 1kHz sine wave signal with a level 10dB higher than the specified input level to record under working bias magnetization, place it in the test environment for 48 hours, and measure the replay output level and the output level after demagnetization and passing through a 1kHz bandpass filter and then replaying. D.(dH)-AB
Wherein, D.—demagnetization rate;
,A——replay output level after 48h placementB——replay output level after demagnetization.
Demagnetization current: On the reference band, record with a 1kHz sine wave at a level 10dB higher than the specified input level, and then demagnetize directly.
Replay this signal, measure the playback output level after passing through the 1kHz bandpass filter, and get the current when 65dB is eliminated, and then increase it by 20% as the demagnetization current.
Additional remarks:
This standard was proposed by the Ministry of Radio, Film and Television. This standard was drafted by the Standardization Planning Institute of the Ministry of Radio, Film and Television. The main drafter of this standard is Chen Chengquan.1-93
VrpB)(dB)
S/N(AM)=20lg AM....
Vel(rp)_(dB)
S/N(PM)--20lg PM
Perform the same measurement on the reference band, subtract the obtained reference value from the measured value of the measured band, and express it in dB. 6.2.6 Dropout
Use the signal waveform a and record it with the reference video current I, then replay it. Within 1 minute, the number of drops above 16dB is measured with a dropout counter. 6.2.7 Freeze characteristic
H(6.4μs) and drop
Use the signal waveform to record it, replay it in the freeze state, record the replayed RF output level with a recorder, and measure the time when the signal level drops to half of the original level.
6.2.8 Sound working bias
Record a 1kHz sine wave at a level 10dB lower than the specified input level, and gradually increase the bias current to record. In the playback path, find the bias current with the maximum output, and calculate the sound working bias according to the following formula IA-A×100
Where: A—Bias current at the minimum input level; A. \--Bias current at the maximum output of the reference band. The bias current at the maximum output level is obtained according to Figure 6. 0.5dB
Bias power supply
6.2.9 Sound sensitivity
Record a 1kHz sine wave signal at the specified input level with working bias, and use a level meter to measure the playback output level, and subtract it from the output current of the reference band under the same conditions, expressed in dB. 6.2.10 Sound sensitivity non-uniformity
Record a 1kHz sine wave signal at the specified input voltage over the entire length of the tape under the working bias, observe the output level, find the maximum and minimum values, and express the difference in dB. 6.2.11 Sound frequency characteristics
Record a 1kHz and 10kHz sine wave signal at 10dB lower than the specified input level under the working bias, then replay them, measure their re-excitation output levels with a level meter, and find the deviation relative to the 1kHz output level. GB/T 14854. 1-93
Carry out the same measurement on the reference tape, and also find the playback deviation. Calculate the sound frequency characteristics according to the following formula: FF (dB) = BB.
Where: B——playback output deviation when testing on the tested tape; B. Playback output deviation when testing on the reference tape. 6.2.12 Sound distortion
Record a 1kHz sine wave signal at a level 6dB higher than the specified input level, and then replay it. Measure the third harmonic and express it as a percentage relative to the original signal.
6.2.13 Sound signal-to-noise ratio
Record the sound at the specified input level and 1kHz sine wave signal under working bias. Measure the playback output level of this signal and the playback output level through the auditory compensation network when there is no signal, and calculate the signal-to-noise ratio (S/N) using the following formula: (S/N), (dB) = AB
Where: A——playback output level when there is a signal (dB) B——playback output level when there is no signal (dB). The characteristics of the auditory compensation network should conform to the A-weighted characteristics. 6.2.14 Copy effect
Use a 1kHz sine wave signal with a level 6d13 higher than the specified input level to record, record once every 10 pictures or so, and the length of each record is about 1/3 to 1/2 of a circle. Do not return before replaying. After placing it in the test environment for 48 hours, rewind the tape and play it through a 1kHz bandpass filter. Use a level recorder to record only the output level (recording pen speed 300mm/s), and read the difference between the signal level and the copy level from the recording paper.
6.2.15 Demagnetization rate
Use a 1kHz sine wave signal with a level 10dB higher than the specified input level to record under working bias magnetization, place it in the test environment for 48 hours, and measure the replay output level and the output level after demagnetization and passing through a 1kHz bandpass filter and then replaying. D.(dH)-AB
Wherein, D.—demagnetization rate;
,A——replay output level after 48h placementB——replay output level after demagnetization.
Demagnetization current: On the reference band, record with a 1kHz sine wave at a level 10dB higher than the specified input level, and then demagnetize directly.
Replay this signal, measure the playback output level after passing through the 1kHz bandpass filter, and get the current when 65dB is eliminated, and then increase it by 20% as the demagnetization current.
Additional remarks:
This standard was proposed by the Ministry of Radio, Film and Television. This standard was drafted by the Standardization Planning Institute of the Ministry of Radio, Film and Television. The main drafter of this standard is Chen Chengquan.A——Replay output level after 48h B——Replay output level after demagnetization.
Demagnetization current: On the reference tape, record with a 1kHz sine wave at a level 10dB higher than the specified input level, and then demagnetize directly.
Replay this signal, measure the playback output level after passing through the 1kHz bandpass filter, and get the current when 65dB is eliminated, and then increase it by 20% as the demagnetization current.
Additional remarks:
This standard was proposed by the Ministry of Radio, Film and Television. This standard was drafted by the Standardization Planning Institute of the Ministry of Radio, Film and Television. The main drafter of this standard is Chen Chengquan.A——Replay output level after 48h B——Replay output level after demagnetization.
Demagnetization current: On the reference tape, record with a 1kHz sine wave at a level 10dB higher than the specified input level, and then demagnetize directly.
Replay this signal, measure the playback output level after passing through the 1kHz bandpass filter, and get the current when 65dB is eliminated, and then increase it by 20% as the demagnetization current.
Additional remarks:
This standard was proposed by the Ministry of Radio, Film and Television. This standard was drafted by the Standardization Planning Institute of the Ministry of Radio, Film and Television. The main drafter of this standard is Chen Chengquan.
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