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4.24.2
4.24.2
4.2
DNVDNV
DNVDNV
DNV
-33 Calibra-33 Calibra
-33 Calibra-33 Calibra
-33 Calibra
tiontion
tiontion
tion
All calibration voltages are factory set and will rarely change. The methods for checking gauge
calibration are detailed below:
4.2.14.2.1
4.2.14.2.1
4.2.1
Reference CheckReference Check
Reference CheckReference Check
Reference Check
The DNV-33D incorporates a quick reference check reading. To utilize this feature the front
panel switch must be in the TEST position. In this position the digital display should read “400”
(+3). If it does not read this the calibration GAIN pot should be adjusted to bring the reading
back to “400”. This will bring the gauge back on the standard average calibration curve.
NOTE: The signal output will change when the switch is put in this position and the set points
may trip.
Pump the gauge tube down to hard vacuum. Set the front panel switch to the ‘CAL’ position.
Adjust the ‘CAL’ pot in the rear of the unit for 000 on the display. If there is a midscale refer-
ence available to the system, see section 4.2.3 on recalibration. Calibration is complete for use
with the standard average curve.
4.2.24.2.2
4.2.24.2.2
4.2.2
RecalibraRecalibra
RecalibraRecalibra
Recalibra
tion for Different Length Gauge tion for Different Length Gauge
tion for Different Length Gauge tion for Different Length Gauge
tion for Different Length Gauge
TT
TT
T
ube Cablesube Cables
ube Cablesube Cables
ube Cables
A maximum of 100 feet of gauge tube cable can be utilized by the DNV-33D. If the cable length
or size (18 gauge) is changed, the unit must be recalibrated. The procedure for recalibration is
described in section 4.2.1.
4.2.34.2.3
4.2.34.2.3
4.2.3
Optimizing Gauge Optimizing Gauge
Optimizing Gauge Optimizing Gauge
Optimizing Gauge
TT
TT
T
ube ube
ube ube
ube
AccuracAccurac
AccuracAccurac
Accurac
yy
yy
y
Individual tubes can be trimmed for best fit upscale on the curve by performing a calibration
adjustment of the gain pot vs. tube output against an accurate reference standard, to do this:
Pump the gauge tube down to hard vacuum. Set the front panel switch to the “CAL” position.
Adjust the “CAL” potentiometer in the rear of the unit until the display reads 000.
Pump the system to a known pressure using a reference in the system. At this pressure, adjust
the gain potentiometer until the display reading matches the reference reading. The unit should
now be calibrated. Best average fit to the curve will occur if 700 mTorr is used for this setting.
Do not use this instrument with another tube unless resetting the gain to “400” per 4.2.1 or
performing the above procedure for the specific tube.
5.0 Notes on Vacuum Measurements
5.1 Effects of Condensable 5.1 Effects of Condensable
5.1 Effects of Condensable 5.1 Effects of Condensable
5.1 Effects of Condensable
VV
VV
V
aporapor
aporapor
apor
ss
ss
s
If the readings of Hastings gauges are to be compared with readings of other types of gauges,
consideration must be given to the possible effects of condensable vapors on other gauges. For
example, none of the many types of McLeod gauges, give correct readings if condensable
vapors such as water, alcohol, acetone, etc., are present in the gauge. The McLeod gauge
operates by compressing residual gases and vapors to obtain a reading, and this compression will
tend to compress vapors that are present. This usally results in pressure reading that is lower
than the actual pressure. Furthermore two different McLeod gauges could be used and both
may have different readings. Both of these readings however could be incorrect if vapors are