Keithley 2002, Calibration Manual

Page: 28 / 114

Performance Verification
1-17
1.8.7 Temperature reading checks
When using thermocouples, the Model 2002 displays tem-
perature by measuring the DC thermocouple voltage, and
then calculating the corresponding temperature. Similarly,
the instrument computes RTD temperature readings by mea-
suring the resistance of the RTD probe and calculating tem-
perature from the resistance value.
Since the instrument computes temperature from DCV and
resistance measurements, verifying the accuracy of those
DCV and resistance measurement functions guarantees the
accuracy of corresponding temperature measurements.
Thus, it is not necessary to perform a comprehensive temper-
ature verification procedure if DCV and resistance verifica-
tion procedures show the instrument meets its specifications
in those areas. However, those who wish to verify that the
Model 2002 does in fact properly display temperature can
use the following procedure to do so.
Selecting the temperature sensor
Follow the steps below to select the type of temperature
sensor:
1. From normal display, press CONFIG then TEMP.
2. Select SENSOR, then press ENTER.
3. Select 4-WIRE-RTD or THERMOCOUPLE as desired,
then press ENTER.
4. Select the type of RTD probe or thermocouple you wish
to test, then return to the CONFIG TEMPERATURE
menu.
5. Select UNITS, then press ENTER.
6. Select DEG-C, then press ENTER.
7. Press EXIT as necessary to return to normal display.
8. Press the TEMP key to place the Model 2002 in the tem-
perature display mode. Refer to further information
below on how to check thermocouple and RTD probe
readings.
Thermocouple temperature reading checks
To check thermocouple readings, simply apply the appropri-
ate DC voltage listed in Table 1-11 to the Model 2002 INPUT
jacks using a precision DC voltage source (such as the one
used to verify DC voltage accuracy in paragraph 1.8.1), and
check the displayed temperature reading. Be sure to use low-
thermal cables for connections between the DC calibrator
and the Model 2002 when making these tests.
NOTE
The voltages shown are based on a 0°C
reference junction temperature. Use the
CONFIG-TEMP menu to set the default
reference junction temperature to 0°C.
Table 1-11
Thermocouple temperature reading checks
Thermocouple
type Applied DC
voltage*
Reading limits
(°C) 1 year,
18°C to 28°C
J -7.659mV
0mV
1.277mV
5.269mV
42.280mV -190.5 to -189.5
-0.5 to +0.5
24.5 to 25.5
99.5 to 100.5
749.5 to 750.0
K -5.730mV
0mV
1.000mV
4.096mV
54.138mV -190.5 to -189.5
-0.5 to +0.5
24.5 to 25.5
99.5 to 100.5
1349.5 to 1350.5
T -5.439mV
0mV
0.992mV
4.278mV
20.255mV -190.5 to -189.5
-0.5 to +0.5
24.5 to 25.5
99.5 to 100.5
389.5 to 390.5
E -8.561mV
0mV
1.495mV
6.319mV
75.621mV -190.6 to -189.4
-0.6 to +0.6
24.4 to 25.6
99.4 to 100.6
989.4 to 990.6
R 0.054mV
0.647mV
4.471mV
20.877mV 7 to 13
97 to 103
497 to 503
1747 to 1753
S 0.055mV
0.646mV
4.233mV
18.503mV 7 to 13
97 to 103
497 to 503
1747 to 1753
B 0.632mV
1.241mV
4.834mV
13.591mV 355 to 365
495 to 505
995 to 1005
1795 to 1805
* Voltages shown are based on ITS-90 standard using 0°C reference
junction temperature. Use CONFIG-TEMP menu to set default reference
junction to 0°C.
NOTE: Reading limits shown do
not include DCV calibrator uncertainty.