Omega CL945A - Page 30

Service Information
4-16
b) For “Measure DC Volts Channel 2”, Calculate the limits of error by
adding/subtracting the value noted in the “Tolerance” column to the value of
the “Standard” column for each setpoint. A PASS result is any “Measurement
Result” value that is equal to or in between the Lower Limit and Upper Limit
error numbers.
10. Enter setup mode,
(1.5s)
and ensure the following parameters are set: units =
“mV” and rAnGE = “Lo”.
11. By using the and/or
keys, adjust the instrument Source to match
each value in Figure 12 in the “Low range”, notating the result from the DMM on
the “Instrument Verification Data Sheet”, Appendix C in “Source DC Volts Channel
1” “Measurement Result” and “Measure DC Volts Channel 2” “Standard” column.
12. Pass/Fail Criteria:
c) For “Source DC Volts Channel 1”, a PASS result is any “Measurement Result”
value that is equal to or in between the Lower Limit and Upper Limit error
numbers.
d) For “Measure DC Volts Channel 2”, Calculate the limits of error by
adding/subtracting the value noted in the “Tolerance” column to the value of
the “Standard” column for each setpoint. A PASS result is any “Measurement
Result” value that is equal to or in between the Lower Limit and Upper Limit
error numbers.
13. To verify the Cold Junction Compensation, (CJC) of the Source, (Channel 1) and
Read, (Channel 2).
14. Place the CL940A in a Controlled Environment
10
along with an accurate
thermometer
11
for one hour to stabilize. Compare CJC readings with the reference
thermometer reading. Display the CJC temperature by pressing
(1.5s)
. The
screen will display “CJC 1” and the current temperature of CJC 1 in °C. Pressing
the key again will display “CJC 2” and the current temperature of CJC 2 in °C.
Notate the results in the “Cold Junction Compensation” section on the Instrument
Verification Data Sheet, placing the Thermometer reading in the “Standard”
column, and the CJC readings in the “Measurement Result” column. Select to
exit.
10
An insulated box inside a calibration lab environment, see Appendix A.
11
An accurate thermometer specification is 2 Sigma uncertainty ≤ .04°C (40mK) at the verification
temperature.