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CALibration
CALibration:TARE
Notes For
Thermocouples
Parameters
Comments
190 HP E1415 Command Reference
CALibration:TARE (@< ch_list >)
channels specified and stores the value in on-board RAM as a calibration constant
for those channels. Future measurements made with these channels will be
compensated by the amount of the tare value. Use CAL:TARE to compensate for
voltage offsets in system wiring and residual sensor offsets. Where tare values need
to be retained for long periods, they can be stored in the module's Flash Memory
(Electrically Erasable Programmable Read Only Memory) by executing the
CAL:STORe TARE command.
For more information See "Compensating for System Offsets" on page 106.
1. You must not use CAL:TARE on field wiring that is made up of
thermocouple wire. The voltage 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
channel. If you inadvertently CAL:TARE a thermocouple wire pair, use
CAL:TARE:RESET to reset all tare constants to zero.
2. 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.
Parameter
Parameter
Name
Type
ch_list
channel list (string)
•
CAL:TARE also 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. As an example assume
that the system wiring to channel 0 generates a +0.1Volt offset with 0Volts (a
short) applied at the Unit Under Test (UUT). Before CAL:TARE the module
would return a reading of 0.1Volts for channel 0. After CAL:TARE (@100),
the module will return a reading of 0Volts with a short applied at the UUT and
the system wiring offset will be removed from all measurements of the signal
to channel 0.
•
Set Amplifier/Filter SCP gain before CAL:TARE. For best accuracy, choose
the gain that will be used during measurements. If you decide to change the
range or gain setup later, be sure to perform another *CAL?.
measures offset (or tare) voltage present on the
Range of
Values
100 - 163
Default
Units
none
Chapter 6
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