VICI D-4-I-VA38-R - Manual (Page 15)

13
Installation
Initial Power-Up
1. Set the discharge gas flow as specified in Figure 4 on page 7.
CAUTION: Always make sure that discharge gas is
flowing before powering up the detector.
2. Apply power to the helium purifier.
3. Turn on the pulser with the toggle switch. The discharge should start
within five minutes. (Once a system has been up and running, the dis-
charge will start within a few seconds.) In a clean system the discharge
will have a peach/pink color. A purple discharge is an indication of
impurities and/or leaks in the discharge gas stream.
4. Set the desired detector temperature.
5. Check the detector standing/background current. For optimum perfor-
mance, detector background current should be < 10 mV. The initial value
may be higher, but as the system bakes out at its operating temperature,
the background current should decrease to the optimum value.
If the standing current reaches an acceptable level, the detector is ready
for use. Follow the Varian instruction manual for operation as an FID.
Troubleshooting High Background Current
If the background current does not drop below 50 mV even after a 12 hour
bakeout, there is either a leak in the system or the column effluent is not
clean. To see if the high background current is due to the column:
1. With a capillary column:
Loosen the knurled nut and pull the column out ~20 mm. Secure the nut.
With a packed column:
Completely disconnect the column from the column inlet tube, leaving the
inlet open.
2. Watch the detector standing/background current.
If the current remains high:
Either the system has a leak in the discharge gas supply line or the
discharge gas has impurities in it. Review “Testing for Leaks” on page 10.
If the current decreases dramatically:
Either the carrier gas supply has leaks and/or contaminants, or the
column is the source of contamination and needs a bakeout.