HP E1313A Manual page 43

Terminal Module
Considerations for
TC Measurements
Scanning Two
Reference Temperature
Channels
42 Field Wiring
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The isothermal characteristics of the HP E1313/E1413 terminal module are
crucial for good TC readings and can be affected by any of the following
factors:
1. The clear plastic cover must be on the terminal module.
2. The thin white mylar thermal barrier must be inserted over the
terminal module connector (HP E1413 only). This prevents airflow
from the HP E1413 module into the terminal module.
3. The terminal module must also be in a fairly stable temperature
environment, and it is best to minimize the temperature gradient
between the HP E1413 module and the terminal module.
4. The VXI mainframe cooling fan filters must be clean and there
should be as much clear space in front of the fan intakes as possible.
5. Recirculating warm air inside a closed-rack cabinet can cause a
problem if the terminal module is suspended into ambient air that is
significantly warmer or cooler. If the mainframe recess is mounted
in a rack with both front and rear doors, closing both doors helps
keep the entire HP E1413 at a uniform temperature. If there is no
front door, try opening the back door.
6. HP recommends that the cooling fan switch on the back of the
HP E1401 Mainframe is in the " High" position. The normal variable
speed cooling fan control can make the internal HP E1413 module
temperature cycle up and down, which affects the amplifiers with
these µV level signals.
The following simple command sequence shows linking channels to
EU conversions to measure the reference temperature of both of the
HP E1313's terminal modules and to measure thermocouples on the
remaining channels.
Link reference temperature to channels 0 and 32 (terminal module 1 and 2).
SENS:REF THER,5000,AUTO,(@100,132) SENS:FUNC:TEMP
Link E type thermocouple measurements to channels 1 - 31 and 33 - 63.
SENS:FUNC:TEMP TC,E,AUTO,(@101:131,133:163)
Define scan list 1 to measure the reference temperature of terminal module 1.
Then measure thermocouples on channels 1 - 31, measure the ref temp of
terminal module 2, then measure thermocouples on channels 33 - 63.
ROUT:SEQ:DEF LIST1,(@100:163)
Now select LIST1 as the current scan list.
ROUT:SCAN LIST1
When the module is triggered, it will scan channels 0 through 63. Since the
first channel on each terminal module measures the reference temperature of
that module, the thermocouple measurements that follow will be referenced
against the temperature of their respective terminal modules.
Chapter 2