Specifications

Terminal Module
Considerations for
Thermocouple
Measurements
The isothermal characteristics of the Terminal Modules 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 (Option 12 only). This prevents airflow from the
VT1419A 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
VT1419A 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 VT1419A at a
uniform temperature. If there is no front door, try opening the back door to
allow the mainframe to cool to the temperature of the Terminal Module.
6. VXI Technology recommends that the cooling fan switch on the back of the
of an Agilent/HP E1401 Mainframe is in the “High” position. The normal
variable speed cooling fan control can make the internal VT1419A module
temperature cycle up and down, which affects the amplifiers with these
microvolt-level signals.
Field Wiring
Configuring the On-Board/Remote Reference Jumpers
Chapter 2 35
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