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digit exponent before being accepted. There are no limit checks on the data; the user is free to choose any
value appropriate to his use of the instrument.
If the command syntax is not met or if the number is out or range, the Digital AVC will respond with the
ASCII codes for <bell>?<CR>, and the command will be ignored.
3.4.4 Reset / Initialize Commands
Command Description Format Notes:
Software Reset /<CR> Reset instrument
Does not reset or overwrite any parameters saved in non-volatile memory (EEPROM).
Autobaud <ctrl-z><CR> Match baud rate currently in use
Device can run at 9600 or 19200 Baud. Set terminal to 9600/N/8/1 or 19200/N/8/1 and type Ctrl-Z.
The <ctrl-z> is entered by holding down the “Ctrl” key while pressing the “z” key when using terminal
emulator program. This character has an ascii code of 26 (decimal) and 1A (hexadecimal).
Device will respond with Device ID (Digital AVC). If this response is not generated, repeat the Ctrl-Z until it
is. The Baud rate will be stored in EEPROM and is remembered on the next power-up.
3.5 Operation and Performance
The Digital AVC will function right “out of the box”. For maximum accuracy refer to the Calibration section
below and perform the calibration procedure.
The simplest and quickest way of checking the operation and performance of a gauge and/or gauge tube,
is to keep a new or known-good gauge tube on hand for use as a reference.
To check operation, install both the reference and suspect gauge tubes in a common vacuum system
(locate the gauge tubes as close as possible to each other), then evacuate the system until a stable base
pressure is obtained. Alternately connect the vacuum gauge to each gauge tube and record its pressure
readings. If the gauge tube-under-test produces a significantly higher pressure reading than the reference
gauge tube, this indicates a calibration shift and is usually the result of contamination (particulate, oil, or
other chemical deposits). You can try to restore calibration of the contaminated gauge tube by cleaning it
internally with an appropriate solvent such as high-purity isopropyl alcohol (flood the interior cavity of gauge
tube gently with solvent and allow it to stand and soak for about 15 to 30-minutes). Drain the contaminated
solvent and let gauge tube dry in ambient air until all of the cleaning solvent has evaporated. To prevent
mechanical damage to the thermopile elements, do not use forced air to dry the gauge tube. Gauge tubes
that remain out of calibration after cleaning should be replaced.
