Getting Started 29Chapter 1
Disabling the
Input Protect
Feature
(Optional)
Disabling the Input Protect feature voids the VT1422A's warranty. The Input
Protect feature allows the VT1422A to open all channel input relays if any input's
voltage exceeds ±19 volts (±6 volts for digital I/O SCPs). This feature will help to
protect the card's Signal Conditioning Plug-ons, input multiplexer, ranging
amplifier and A/D from destructive voltage levels. The level that trips the protection
function has been set to provide a high probability of protection. The voltage level
that is certain to cause damage is somewhat higher. If, in an application, the
importance of completing a measurement run outweighs the added risk of
damage to the VT1422A, the input protect feature may be disabled.
Voids Warranty! Disabling the Input Protection Feature voids the VT1422A's warranty.
To disable the Input Protection feature, locate and cut JM2202. Make a single cut in
the jumper and bend the adjacent ends apart. See following illustration for location
of JM2202.
Disabling
Flash Memory
Access
(Optional)
The Flash Memory Protect Jumper (JM2201) is shipped in the “PROG” position. It
is recommended that the jumper be left in this position so that all of the calibration
commands can function. Changing the jumper to the protect position prevents the
following from being executed:
•The SCPI calibration command CAL:STORE ADC | TARE
•The register-based calibration commands STORECAL and STORETAR
•Any application that installs firmware-updates or makes any other
modification to Flash Memory through the A24 window.
With the jumper in the “PROG” position, one or more VT1422As can be completely
calibrated without removing them from the application system. A VT1422A
calibrated in its working environment will, in general, be better calibrated than if it
were calibrated separate from its application system.
The multimeter used during the periodic calibration cycle should be considered the
calibration transfer standard. Allow Calibration Organization control unauthorized
access to the calibration constants.
If access must be limited to the VT1422A's calibration constants, place JM2201 in
the protected position and cover the shield retaining screws with calibration
stickers. See the following illustration for location of JM2201.