Compensating For System Offsets - HP E1419A User Manual

Creating Conversion
Tables
Summary

Compensating for System Offsets

System Wiring Offsets
Important Note for
Thermocouples
100 Programming the HP E1419A
considered the "reference junction temperature", the channel is linked to this
EU table using the command [SENSe:]FUNCtion:CUSTom:REFerence
[<range>,](@<ch_list>).
This command uses the custom EU conversion to generate the reference
junction temperature as explained in the section Thermocouple Reference
Temperature Compensation on page 3-64.
The HP 1419A comes with an HP VEE example program you can use to
generate custom EU tables. See the "eu_1419.vee" example in Chapter 5 for
more information.
The following points describe the capabilities of custom EU conversion:
•
A given channel only has a single active EU conversion table
assigned to it. Changing tables requires loading it with a
DIAG:CUST:... command.
•
The limit on the number of different custom EU tables that can be
loaded in an HP E1419A is the same as the number of channels.
•
Custom tables can provide the same level of accuracy as the built-in
tables. In fact the built-in resistance function uses a linear conversion
table, and the built -in temperature functions use the piecewise
conversion table.
The HP E1419A can compensate for offsets in your system's field wiring.
Apply shorts to channels at the Unit-Under-Test (UUT) end of your field
wiring, and then execute the CAL:TARE (@<ch_list>) command. The
instrument will measure the voltage at each channel in <ch_list> and save
those values in RAM as channel Tare constants.
•
You must not use CAL:TARE on field wiring that is made up of
thermocouple wire. The voltage that a thermocouple wire pair
generates can not be removed by introducing a short anywhere
between its junction and its connection to an isothermal panel (either
the HP E1419A's Terminal Module or a remote isothermal reference
block). Thermal voltage is generated along the entire length of a
thermocouple pair where there is any temperature gradient along that
length. To CAL:TARE thermocouple wire this way would introduce
an unwanted offset in the voltage/temperature relationship for that
thermocouple. If you inadvertently CAL:TARE a thermocouple wire
pair, see "Resetting CAL:TARE" on page 3-102.
Chapter 3