Calibration
Temperature Source Calibration 4
4-9
Table 4-4. As Found Uniformity Results
UUT
SETPOINT °C
Number of
Samples
Average PRT
Secondary
Reading °C
Average PRT
Primary °C
Uniformity
Error °C =
PRTsec-
PRTprim
Specification
°C
140 °C 40 0.05 °C
100 °C 40 0.05 °C
25 °C 40 0.05 °C
0 °C 40 0.05 °C
−45 °C 40 0.05 °C
−95 °C 40 0.05 °C
Table 4-5. As Found Stability Specifications
SETPOINTS °C Stability 2σ Spec (±°C)
Soak Time
(minutes)
Duration
(minutes)
140 °C 0.015 °C 45 30
0 °C 0.015 °C 45 30
−95 °C 0.015 °C 45 30
Uniformity Alignment 1st Iteration
Perform the 1
st
Uniformity Alignment as follows:
1. Set the UUT SETPOINT temperature to -90 °C and engage the temperature control.
2. Monitor the Stability Status indicator to ensure the heat source is stable. Let the UUT
soak at the -90 °C SETPOINT for 45 minutes after the Stability Status indicator
shows that the temperature is stable (flat line). Measure the ACTUAL gradient,
which is the temperature of the secondary PRT (30 mm probe) minus the temperature
of the primary PRT (0 mm probe). Take the average of 40 samples for each of the
probes. Calculate as follows:
ACTUAL grad = T
30
- T
0
3. Query the UUT gradient sensor reading with this serial command:
SOUR:SENS:GRAD:DATA?
4. Repeat this 40 times to get an average of the gradient sensor reading. This value is
called “UUT grad”. Calculate the Error with this formula:
ERROR
1
= UUT grad – ACTUAL grad
5. If the magnitude of ERROR
1
is less than 0.012, skip to the next Gradient calibration
temperature and repeat the Uniformity Alignment 1
st
Iteration procedure.
6. Query the UUT GRAD 1 calibration parameter as follows:
SOUR:SENS:CAL:GRAD1?
7. Grad 1 is associated with UUT block temperature -90 °C. Calculate the new Grad 1
calibration parameter as follows:
New
GRAD 1
= GRAD 1 – ERROR
1
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