Table of Contents
Advertisement
1575/1590 Thermometer Readout
User's Guide
34
If I only use the internal 100Ω reference resistor, do I need to maintain cali-
bration of the other reference resistors?
If you only use certain internal reference resistors it is not necessary to cali-
brate the unused resistors. For example, if you only use the 1575/1590 for mea-
suring 10 kΩ thermistors there may be no need to calibrate the 1Ω, 10Ω, and
100Ω internal reference resistors. Likewise, if the 1575/1590 will only be used
with external reference resistors you do not need to calibrate any of the internal
reference resistors. Nevertheless, you should still periodically verify the resis-
tance ratio accuracy of the 1575/1590. If you choose to maintain only a limited
calibration take necessary precautions to ensure that the instrument will not be
used outside its calibrated ranges.
If two probes are connected to the 1575/1590, is current supplied to both at the
same time?
During a measurement, the 1575/1590 drives only the probe and reference re-
sistor with current. If two probes are connected and measured alternately while
using one of the internal reference resistors, the current will alternate between
the two probes. It is possible that this could cause slight error in the measure-
ment if self-heating is significant. Self-heating error can be evaluated with sim-
ple tests (see Section 7.4.4.3). When using the 2590 Scanner with the 1590 this
problem can be avoided since the 2590 incorporates an independent standby
current source for each channel.
Can the 1575/1590 calculate ITS-90 coefficients?
Yes. The ITS-90 calibration feature allows you either measure resistance data
or enter previously obtained values to calculate ITS-90 coefficients (see Section
7.4.4.2.8).
Can the 1575/1590 generate Callendar-Van Dusen, IPTS-68, or thermistor
coefficients?
The 1575/1590 is not able to calculate coefficients for characterizations other
than ITS-90. The 1575/1590 can be used to obtain resistance and temperature
measurements for calibration, but calculation of coefficients for Callendar-Van
Dusen, IPTS-68, or thermistor sensors must be done with external software.
Can the 1575/1590 convert IPTS-68 or Callendar-Van Dusen coefficients to
ITS-90 coefficients?
The 1575/1590 can be used to calculate ITS-90 coefficients from IPTS-68 or
Callendar-Van Dusen coefficients using the following procedure: First, you
must set up a probe record with your IPTS-68 or Callendar-Van Dusen coeffi-
cients (use EDIT PROBE, see Section 7.4.3.2.2). Second, use the CONV TEST
function to enter resistances and obtain temperatures near each of the required
ITS-90 calibration points for Range 4 and Range 7 or 8 (Section 7.4.4.2 and
7.4.4.5). Carefully note the resistances and corresponding temperatures. Third,
use EDIT PROBE to select ITS-90 and the appropriate subranges (Section
7.4.3.2.1) for one probe record (there's no need to enter values for A[4], B[4],
Hide quick links:
Advertisement
Table of Contents
