Prostat CVM-780 - XI. Instrument Maintenance; Instrument Maintenance

19
Rev. D / January 2015
CVM-780 Contact Voltmeter
1. If the PGA-710 or PGA-710B and CVM-780 zero seng are the same measurement recordings
can be made
2. If they are not the same, stop the Preview and proceed as follows.
H. Adjust the CVM-780 carefully to display 000 on its LED.
I. Select the Autoanalysis  drop down menu and open the  window. In the Volt-
age secon:
a. Click  buon, then
b. Click  buon, then
c. Click  buon to close the window and acve the zero reset
J. Start the Autoanalysis  and compare the  to the CVM-780’s LED
voltage; they should both be 000 ±1 volt.
As measured voltage increases, there is a small deviaon between CVM-780 displayed voltage and PGA-
710 or PGA-710B recorded voltage. It may be as low as ±2 volts below ±200 volts and increase to 5 or 6
volts deviaon at ±500 volts. The fact that the measurement can be made relavely accurately at that
level is signicant; the 5 to 6 volts deviaon is generally not an important error.
 
Maintenance ps and care of the CVM-780 follow.
A. There are no user adjustments or maintenance items inside the instrument case or probe assem-
bly. Do not open the case or probe as this will damage the instrument and VOID its warranty. War-
ranty seals are a reminder not to open these units.
B. Clean the surfaces of the instrument case and probe assembly with a low linng, non-abrasive
cloth lightly dampened with 70% soluon of alcohol and 30% water.
C. It is important to keep the front probe assembly black insulator very clean. Surface contaminants
on this insulator will cause voltage leakage to the probe’s grounded metal surface resulng in
unstable measurements. Use a low linng, non-abrasive cloth lightly dampened with 70% soluon
of alcohol and 30% water to clean the insulator. Alcohol prep wipes are useful for removing nger
oils and contaminants.
D. Excessive voltage dri while the probe is “oang” – that is, while not grounded or making a
contact measurement – may be caused by a large charge on the black insulator used for probe p
mounng. Insulator surface charge is caused by installing and removing the probe p cover. Exces-
sive “twisng” of the p cover increases this charge. This charge does not aect instrument ac-
curacy, but may become distracng. If desired remove this charge by exposing the probe assembly
to a balanced bench top ionizer. Note that the ionizer’s oset voltage (unbalance) will be displayed
on the CVM-780’s LED.