We frequently get questions about our gas proportional detectors, and are glad to offer information on how we "check out" this product. In the following example, we will demonstrate the check-out procedure for the Ludlum Model 43-68 gas proportional detector.
The equipment necessary to begin includes a Ludlum counter (scaler or portable survey meter), a pressurized container of P-10 counting gas (90% argon, 10% methane approximately 2000 psi or 13,790 kPa), a dual stage regulator supplied with a needle valve and input/output flow meters, and a supply of calibrated sources (alpha, beta/gamma). Please note that both quick connects (male and female) are double ended shut off valves. Caution: If either the output quick connect or the input quick connect attachment is removed the gas must be turned off.
The gas proportional detector can be flushed at a high rate (4 - 5 inches of water) by attaching the gas input quick connect and by removing the hose from the output quick connect which allows the gas to flow freely. Flush for approximately 15 minutes (larger detectors may require a longer flush period), turn gas off, reconnect hose to quick connect, and set gas flow to 120 cc/min. The output should read approximately the same cc/min as the input; if not, check the detector for gas leakage. The detector should now be ready to check or plateau if the preceding procedures have been followed.
To check the detector, set the counting instrument's threshold adjustment to 10 mV sensitivity. Connect the detector to the counting instrument and begin the plateau. The typical operating voltage should be 1000 - 1200 volts for alpha and 1600 - 1700 volts for beta/gamma.