Troubleshooting
4-3
When “Gas Corr” has been selected, the up and down arrow keys can be used to set a new value to
the flashing digit. The “Enter” key will advance the flashing through the digits, saving the new value
after the last digit has been set.
Emission mA
The Emission current is set to 4.00 mA as a default. The emission current will remain constant (4 mA) as
long as the pressure is less than 1.3 x 10
-3
Pa/1 x 10
-5
Torr. The senTorr automatically reduces the cur-
rent by a factor of 10 when the pressure is greater than 6.6 x 10
-3
Pa / 5 x 10
-5
Torr. Thus, the emission
current would drop to 0.4 mA. This promotes an extended pressure range measurement capability and/or
prolongs tube life by protecting the filament.
Emission current can be adjusted from 10 µA to 9.99 mA through the keypad on the front panel of the
senTorr unit. One reason why a user might possibly consider lowering the emission current is to pre-
vent a small fluctuation in a pressure reading that may occur when operating just below 1.3 x 10
-3
Pa/
1 x 10
-5
Torr and just above 6.6 x 10
-3
Pa / 5 x 10
-5
Torr. If emission current is adjusted to < 1 mA, the
current will remain constant throughout the entire pressure range.
Another reason why a user might consider lowering the emission current pertains to the applications
that require higher pressure readings from the gauge tube. The lower the emission, the higher in pres-
sure the tube is able to measure. This also applies in the opposite direction; the higher the emission
current is raised, the lower in pressure the tube can measure.
Programming Emission mA
Enter the Program mode by pressing the “Option Select” key. The first available parameter, beginning
from the top of the column and depending on the senTorr model and options installed, will flash in the
appropriate gauge display. Repeatedly pressing the “Option Select” key will advance through the para-
meters, returning the unit to the Run mode after the last key press.
When “Emis mA” has been selected, the up and down arrow keys can be used to set a new value to
the flashing digit. The “Enter” key will advance the flashing through the digits, saving the new value
after the last digit has been set.
Sensitivity
Default Sens
Tube
3325/Pa
25/T
UHV 24
1330/Pa
10/T
571, 572, 563
665A/Pa
5 A/T
525, 524
1064/Pa
8/T
580, 564
133A/Pa
1 A/T
Inv Mag CC
To improve the accuracy of pressure measurements, sensitivity can easily be adjusted to match gauge
tube calibration.