106
Programming the HP E1415 for PID Control
Compensating for System Offsets
System Wiring Offsets
The HP E1415 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.
Important Note for
Thermocouples
•
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 E1415’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 107.
•
You should use CAL:TARE to compensate wiring offsets (copper
wire, not thermocouple wire) between the HP E1415 and a remote
thermocouple reference block. Disconnect the thermocouples and
introduce copper shorting wires between each channel’s HI and LO,
then execute CAL:TARE for these channels.
Residual Sensor Offsets
To remove offsets like those in an unstrained strain gage bridge, execute the
CAL:TARE command on those channels. The module will then measure the
offsets and as in the wiring case above, remove these offsets from future
measurements. In the strain gage case, this "balances the bridge" so all
measurements have the initial unstrained offset removed to allow the most
accurate high speed measurements possible.
Operation
After CAL:TARE <ch_list> measures and stores the offset voltages, it then
performs the equivalent of a *CAL? operation. This operation uses the Tare
constants to set a DAC which will remove each channel offset as "seen" by
the module’s A/D converter.
The absolute voltage level that CAL:TARE can remove is dependent on the
A/D range. CAL:TARE will choose the lowest range that can handle the
existing offset voltage. The range that CAL:TARE chooses will become the
lowest usable range (range floor) for that channel. For any channel that has
been "CAL:TAREd" Autorange will not go below that range floor and
selecting a manual range below the range floor will return an Overload value
(see the table “Maximum CAL:TARE Offsets” on page 107).
As an example assume that the system wiring to channel 0 generates a +0.1
Volt offset with 0 Volts (a short) applied at the UUT. Before CAL:TARE
Summary of Contents for VXI 75000 C Series
Page 2: ......
Page 16: ...16 ...
Page 18: ......
Page 30: ...30 Getting Started Chapter 1 Notes ...
Page 32: ...32 Field Wiring Chapter 2 Figure 2 1 Channel Numbers at SCP Positions ...
Page 44: ...44 Field Wiring Chapter 2 Figure 2 11 HP E1415 Terminal Module ...
Page 54: ...54 Field Wiring Chapter 2 Notes ...
Page 61: ...Programming the HP E1415 for PID Control 61 Chapter 3 Programming Overview Diagram ...
Page 136: ...136 Creating and Running Custom Algorithms Chapter 4 Notes ...
Page 152: ...152 Algorithm Language Reference Chapter 5 Notes ...
Page 304: ...304 HP E1415 Command Reference Chapter 6 Command Quick Reference Notes ...
Page 308: ...308 Specifications Appendix A Thermocouple Type E 200 800C SCPs HP E1501 02 03 ...
Page 309: ...Specifications 309 Appendix A Thermocouple Type E 200 800C SCPs HP E1508 09 ...
Page 310: ...310 Specifications Appendix A Thermocouple Type E 0 800C SCPs HP E1501 02 03 ...
Page 311: ...Specifications 311 Appendix A Thermocouple Type E 0 800C SCPs HP E1509 09 ...
Page 312: ...312 Specifications Appendix A Thermocouple Type E Extended SCPs HP E1501 02 03 ...
Page 313: ...Specifications 313 Appendix A Thermocouple Type E Extended SCPs HP E1508 09 ...
Page 314: ...314 Specifications Appendix A Thermocouple Type J SCPs HP E1501 02 03 ...
Page 315: ...Specifications 315 Appendix A Thermocouple Type J SCPs HP E1508 09 ...
Page 316: ...316 Specifications Appendix A Thermocouple Type K SCPs HP E1501 02 03 ...
Page 317: ...Specifications 317 Appendix A Thermocouple Type R SCPs HP E1501 02 03 ...
Page 318: ...318 Specifications Appendix A Thermocouple Type R SCPs HP E1508 09 ...
Page 319: ...Specifications 319 Appendix A Thermocouple Type S SCPs HP E1501 02 03 ...
Page 320: ...320 Specifications Appendix A Thermocouple Type S SCPs HP E1508 09 ...
Page 321: ...Specifications 321 Appendix A Thermocouple Type T SCPs HP E1501 02 03 ...
Page 322: ...322 Specifications Appendix A Thermocouple Type T SCPs HP E1508 09 ...
Page 323: ...Specifications 323 Appendix A 5K Thermistor Reference SCPs HP E1501 02 03 ...
Page 324: ...324 Specifications Appendix A 5K Thermistor Reference SCPs HP E1508 09 ...
Page 325: ...Specifications 325 Appendix A RTD Reference SCPs HP E1501 02 03 ...
Page 326: ...326 Specifications Appendix A RTD SCPs HP E1501 02 03 ...
Page 327: ...Specifications 327 Appendix A RTD SCPs HP E1508 09 ...
Page 328: ...328 Specifications Appendix A 2250 Thermistor SCPs HP E1501 02 03 ...
Page 329: ...Specifications 329 Appendix A 2250 Thermistor SCPs HP E1508 09 ...
Page 330: ...330 Specifications Appendix A 5K Thermistor SCPs HP E1501 02 03 ...
Page 331: ...Specifications 331 Appendix A 5K Thermistor SCPs HP E1508 09 ...
Page 332: ...332 Specifications Appendix A 10K Thermistor SCPs HP E1501 02 03 ...
Page 333: ...Specifications 333 Appendix A 10K Thermistor SCPs HP E1508 09 ...
Page 334: ...334 Specifications Appendix A Notes ...
Page 346: ...346 Glossary Appendix C Notes ...
Page 388: ...388 Generating User Defined Functions Appendix F Notes ...