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Technical Articles
Over the years, Ludlum Measurements has written several technical articles in support of our products. These articles cover topics such as troubleshooting and repair tips, calibration techniques, and other information related to radiation detection and instrumentation.
Survey Meters and Detectors
At some point you may wish to use a different detector with your survey meter than the detector the instrument was originally calibrated with. Unfortunately, this can cause issues because not all detectors operate at the same high voltage or use equivalent meter scales. Using a survey meter and a detector that have not been configured to be used together can lead to inaccurate radiation measurements.
Adjusting the High Voltage on LMI Instruments
One of the most common service problems is the maladjustment of the detector high voltage setting. We receive many calls from users who have attempted to trouble-shoot their instrument with a "high Impedance" voltmeter. This usually results with the problem of not being able to adjust the high voltage above 450 V. The reason for this problem is the "high impedance" voltmeter typically has an 11 MΩ output impedance and will overload on resistive loads below 60 MΩ.
Determining Detector Operating Voltage
Many of our customers inquire about the procedure we use to check the operating voltage of scintillation or proportional type detectors. We call this process “to run a plateau”. Hopefully, the following will help to answer a few of these questions.
Connectors
Have you ever really needed an extra probe or cable badly, and after receiving it, found it had the wrong connector?
If the answer is yes, then this problem can be solved with a little help from you.
Calibration Tips: Gas Proportional Detectors
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.
Repair Tips - Battery Compartments and Cables
The majority of problems we encounter with returned instruments in the Ludlum Repair Department require simple solutions. Dirty or corroded contacts (especially battery contacts), damaged cables, loose connections, and other types of mechanical problems are the leading cause of instrument failure. Although electronic component failure is a possibility, it is infrequent in comparison.
Condensing Humidity
Occasionally a customer may experience a problem with condensing humidity causing dew or frost inside the instrument. Presume that your instrument is in your office which has a temperature of 72 °F and a relative humidity of 40% and you take the instrument outdoors where the temperature is 40 °F. When the instrument "cools down" to 45 °F, dew will form inside the instrument and possibly cause the instrument to malfunction. In the same indoor temperature as above with an outdoor temperature of 20 °F, the dew will turn to frost when the instrument "cool down" temp is 32 °F.
Operating Scintillation Detectors at 900 Volts
Many of our customers inquire about using scintillation and GM detectors interchangeably with the same instrument. To make this possible, a few extra steps must be taken because of the difference in operating voltages of these two types of detectors.
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