Section 10: Calibrating the Model 9100: Calibration Mode
10.2-9
Final Width = 215mm
Continued overleaf
10.2.5.4
CJC Pod Identification
Because a CJC pod is calibrated together with a particular host 9100 unit, and the pod's
correction data is held in the host's non-volatile memory, traceability is maintained only
when the pod is used with that host. Where an organisation holds more than one 9100
and pod, there is a need to identify each pod's host 9100.
To encourage user organisations to register the association of each pod with a particular
9100, the label affixed to each pod has the serial number of the pod, plus a blank space
for recording the serial number of the 9100 with which it is calibrated.
Part of the calibration procedure in paras 10.2.5.7, gives an instruction to record the
serial number of the host 9100 in the space on the label.
10.2.5.5
Equipment Requirements
To calibrate using front panel controls, the procedure requires a traceably-calibrated
Resistance Temperature Detector (RTD) equipped with a special 0.385
Ω
/
°
C, 3mm
diameter Platinum Resistance Thermometer (PRT Sensor Assembly
—
Fluke
part
no.
401233 — traceably calibrated to an accuracy of
±
10m
Ω
at 100
Ω
). The test uncertainty
ratio of this combination over the 9100 RTD function specification must be at least 3:1,
at the required calibration temperature between 0
°
C and 50
°
C.
Alternatively,
the
same
PRT
can
be
used
with
a
DMM (e.g:
Fluke
Model 1271), whose
100
Ω
or 1k
Ω
range is traceably-calibrated at 100
Ω
to an accuracy of better than 0.013
Ω
.
The source current must be limited to 1mA
±
20% to avoid self-heating errors in the PRT.
A formula for conversion from resistance to temperature is given with the procedure in
paras. 10.2.5.7.
For remote calibration,
the
Fluke
Model
4950
Multifunction
Transfer
Standard
can
be
used, in conjunction with the MTS Control Software, to support this procedure
automatically.
10.2.5.6
Error Reduction
Any errors in taking external measurements of the Reference Junction temperature can
be attributed to environmental conditions and/or bad practice. To minimize these errors
the following techniques should be implemented:
•
Minimize all handling of the module, PRT element and leads, hence avoiding
variations of temperature.
•
Throughout all measurements shield the Reference Junction module from draughts,
especially from fans in the vicinity.
•
Before recording any results, be patient and allow the readings to stabilize.