Is this a 50 or 60 hrz? The timer I think is fixed in the CPU. The MAS meter has calibration and is related to MA. If your Physicist uses the panel MAS meter then accuracy must be check with an external calibrated MAS meter. Once its OK then MAS is use in relation to fix-time to calibrate MA (filament).
Where do you have the problem? in short exposures time 300ms? If you have in short, there is a parameter to calibrate depending of the lenth of the HV cables.
Generator settings:
kVp (80), mA (320), FS (L), T (50ms) = T (44.9ms) Fail
kVp (80), mA (400), FS (L), T (42ms) = T (36.5ms) Fail
Both are more than 10% off.
Where do you have the lack of accuracy? , in short times less than 100ms ?or in long times >200 ms?. If you have in short times, there is a parameter calibration to compensate HV cables length.
Received Pysicists report. Exposure Timer Accuracy
kVp (80) mA (320) FS (L) T (50ms) = Fail T (44.9ms)
kVp (80) mA (400) FS (L) T (42ms) = Fail T (36.5ms)
Both more than 10% off.
The equipment is out of tolerance in short times by aprox 11% almost in spec 10%,I think system should be in spec if tou try times in 80kv 100mA 50ms and 80kv 100ma 42 ms, if you are out with 320ma and 400ma is spatial charge due to the ma. You can try this steps.
In calibration section 10 : test line sync and phase reversal check page 3-36.
In calibration section 15 : Electron cooling compensation page 3-58. You can change the parameter in each ma station and see if the time increases or decreases. Try to tweak !! it´s your only choice.
For tube 1 address C1CB electronC 320ma
address C1CC electronC 400ma
enable electron Cooling
Note :
As far as I know you can not modify the exposure time in an MVP micro but you can modify the waveform of ma and Kv (and try to cheat the non invasive meter), Mvp micro is a monophase generator the HV waveform are pulses is not a square like in new generators, so when you measure time with a non invasive method is not the same as using a scope.
The Mvp micro is counting pulses so, in 60 hz the minimum exposure time is 16ms (one pulse) the half is 8.3 ms I think this is the minimum error
Note 2 :
Reading post from Gerardo Millena he is right system must be in specs
In sm table 3-24, pag 3-64 time tolerance is +- 0.0083 sec (8.3 ms) for exposures 0.016 to 0.4 sec
Thanks Charlie, also He could try to simply lower slightly the 320 and 400ma without going out of spec. this way you'll have a longer KV decay I think. I wonder what's the non invasive device they are using since others requires at least 100ms exposure to read. HV bleeder - scope would give more accuracy.
Hello, Thanks for the info.
Really not to familiar with this system but whiling to learn. The only manual I have is MVP Micro Service Manual Volume 1 1987 GE. Do I need any other manuals ?
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Jeremiah Kiblin
GE MVP Micro - Timer Accuracy OFF
July 31, 2014 08:49
The Physicist found the timer accuracy does not meet MFG specs. Anybody know how to re-calibrate generator to improve the timer accuracy ?
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gerardo millena
re: GE MVP Micro - Timer Accuracy OFF
August 04, 2014 08:51
Is this a 50 or 60 hrz? The timer I think is fixed in the CPU. The MAS meter has calibration and is related to MA. If your Physicist uses the panel MAS meter then accuracy must be check with an external calibrated MAS meter. Once its OK then MAS is use in relation to fix-time to calibrate MA (filament).
to rate and post a comment
Charlie Britt
re: GE MVP Micro - Timer Accuracy OFF
August 04, 2014 08:51
Where do you have the problem? in short exposures time 300ms? If you have in short, there is a parameter to calibrate depending of the lenth of the HV cables.
to rate and post a comment
Jeremiah Kiblin
re: re: GE MVP Micro - Timer Accuracy OFF
August 04, 2014 02:53
Generator settings:
kVp (80), mA (320), FS (L), T (50ms) = T (44.9ms) Fail
kVp (80), mA (400), FS (L), T (42ms) = T (36.5ms) Fail
Both are more than 10% off.
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Charlie Britt
re: GE MVP Micro - Timer Accuracy OFF
August 04, 2014 08:56
Where do you have the lack of accuracy? , in short times less than 100ms ?or in long times >200 ms?. If you have in short times, there is a parameter calibration to compensate HV cables length.
to rate and post a comment
Charlie Britt
re: GE MVP Micro - Timer Accuracy OFF
August 04, 2014 08:56
If you have in short times less than 100 ms there is a calibration factor for HV cables length
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Jeremiah Kiblin
re: GE MVP Micro - Timer Accuracy OFF
August 04, 2014 02:53
Received Pysicists report. Exposure Timer Accuracy
kVp (80) mA (320) FS (L) T (50ms) = Fail T (44.9ms)
kVp (80) mA (400) FS (L) T (42ms) = Fail T (36.5ms)
Both more than 10% off.
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gerardo millena
re: re: GE MVP Micro - Timer Accuracy OFF
August 05, 2014 10:07
On section 17 (HHS Testing) page 3-113 says for 0.016 to 1 sec accuracy is +/- 0.0167 sec. Not sure if this would help.
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Charlie Britt
re: re: re: GE MVP Micro - Timer Accuracy OFF
August 06, 2014 08:10
The equipment is out of tolerance in short times by aprox 11% almost in spec 10%,I think system should be in spec if tou try times in 80kv 100mA 50ms and 80kv 100ma 42 ms, if you are out with 320ma and 400ma is spatial charge due to the ma. You can try this steps.
In calibration section 10 : test line sync and phase reversal check page 3-36.
In calibration section 15 : Electron cooling compensation page 3-58. You can change the parameter in each ma station and see if the time increases or decreases. Try to tweak !! it´s your only choice.
For tube 1 address C1CB electronC 320ma
address C1CC electronC 400ma
enable electron Cooling
Note :
As far as I know you can not modify the exposure time in an MVP micro but you can modify the waveform of ma and Kv (and try to cheat the non invasive meter), Mvp micro is a monophase generator the HV waveform are pulses is not a square like in new generators, so when you measure time with a non invasive method is not the same as using a scope.
The Mvp micro is counting pulses so, in 60 hz the minimum exposure time is 16ms (one pulse) the half is 8.3 ms I think this is the minimum error
Note 2 :
Reading post from Gerardo Millena he is right system must be in specs
In sm table 3-24, pag 3-64 time tolerance is +- 0.0083 sec (8.3 ms) for exposures 0.016 to 0.4 sec
Simply try.
to rate and post a comment
gerardo millena
re: re: re: re: GE MVP Micro - Timer Accuracy OFF
August 06, 2014 08:42
Thanks Charlie, also He could try to simply lower slightly the 320 and 400ma without going out of spec. this way you'll have a longer KV decay I think. I wonder what's the non invasive device they are using since others requires at least 100ms exposure to read. HV bleeder - scope would give more accuracy.
to rate and post a comment
Jeremiah Kiblin
re: re: re: re: GE MVP Micro - Timer Accuracy OFF
August 07, 2014 10:28
Hello, Thanks for the info.
Really not to familiar with this system but whiling to learn. The only manual I have is MVP Micro Service Manual Volume 1 1987 GE. Do I need any other manuals ?
to rate and post a comment