How often should I send my electrometer in for calibration?
At what times should I zero my electrometer?
How can I reduce my chances of electrometer channel failure?
My electrometer’s display has gone blank, what should I do?
In general, how do I properly zero the electrometer + extension cable + ion chamber system?
What are the differences between the MAX 4000 and MAX 4001 Electrometers?
How do I zero my electrometer?
If the FAQs did not answer your question
Q How often should I send my electrometer in for calibration?
- The IEC (International Electrotechnical Commission) recommends electrometer calibration every two years to assure optimal performance.
- IEC 60731 IEC 60731 – Medical electrical equipment – Dosimeters with ion chambers such as used in radiotherapy.
- IEC 61674 IEC 61674 – Medical electrical equipment – Dosimeters with ion chambers and/or semi-conductor detectors as used in X-ray diagnostic imaging.
- Standard Imaging works with the University of Wisconsin ADCL to perform calibrations, but also provides free inspection and testing services, as well as expedited repair service, if necessary. Click here to initiate a calibration and service appointment.
- Standard ImagingStandard Imaging’s goal is a two week turn around upon receipt of equipment, although actual time may vary depending on the UW ADCL’
Q I am seeing drift or leakage with my electrometer + ion chamber system. Is there something wrong with my chamber, electrometer, or both?
- You may need to zero your electrometer. Click here to read more.
- Check all cables for crimping or damage, and allow settling time after setup or movement. Crimping, damage, and significant movement such as unwinding from a spool can cause or contribute to system leakage.
- It is recommended to use as short of an extension cable as possible. In general, the longer the cable, the longer the signal settling time and the longer for bias voltage to dissipate.
- A common cause is dust that has collected on the inside of the connector on the chamber cable, extension cable, and/or electrometer. Standard Imaging has created a tech note containing a triax connector cleaning procedure. This procedure should be periodically performed or whenever there are concerns of drift or leakage. Heavier product use may require more frequent cleanings. In addition, utilize dust caps on chamber and electrometer triax connectors whenever possible.
- Click here to view the connector cleaning tech note.
- Determine which part of the electrometer + extension cable + chamber system is exhibiting the leakage or causing drift, in this order of troubleshooting:
- Electrometer: With nothing attached and the dust cap in place, warm up the electrometer and check for stability. Perform a 60 second charge collection and determine if the signal shown is within the electrometer’s stated acceptable limits.
- Extension cable: If it has been determined that the electrometer is not exhibiting leakage or drift, connect the desired extension cable (with no bias applied when connecting, no chamber attached, but dust cap on), and determine if the signal level settles in the cable manufacturer’s stated settling time estimate.
- Ion Chamber: If it has been determined the electrometer is not exhibiting leakage or drift, connect the desired chamber directly to electrometer (with no bias applied at time of connection and no extension cables attached), and determine if the signal level settles within the chamber manufacture’s stated settling time estimate and the leakage of the chamber is within the manufacture’s stated acceptable limits.
- If these techniques do not resolve the drift or leakage problems, contact your Standard Imaging representative or your ion chamber’s manufacturer for assistance. Click here for contact information.
Q At what times should I zero my electrometer?
- Zeroing should be performed after the signal level stabilizes following any of the changes listed below (see electrometer user manual for specific instructions):
- At system startup, after completion of warm-up sequence
- When a new range of operation (high or low) is selected
- After a chamber is connected and is allowed at least 5 minutes to stabilize
- Each component (chamber, extension cable, etc.) added to the system may introduce an offset to the signal level. When the system stabilizes, perform a system zero to clear this offset.
- After any time a significant change is made to temperature, pressure, or movement in the system setup
- Do not perform a system zero if signal level trends in either direction, wait until a stable signal level is achieved before performing a system zero
Q How can I reduce my chances of electrometer channel failure?
- Do not connect or disconnect a chamber from the electrometer when bias voltage is applied. It is advised to wait about 30 seconds (a longer wait is recommended for longer chamber extension cables) before reconnecting a chamber to which bias has recently been applied.
- Use as short of an extension cable as possible. In general, the longer the cable, the longer the signal settling time and the longer for bias voltage to dissipate.
- Consider ramping up bias levels incrementally, especially if switching polarity from a large voltage level. For example, ramp slowly from -300 to 0 to 300 volts.
- Have your Standard Imaging electrometer serviced and inspected at time of calibration by Standard Imaging. Standard Imaging works with the University of Wisconsin ADCL to perform calibrations, but also provides free inspection and testing services, as well as expedited repair service, if necessary. Click here to initiate a calibration and service appointment.
Q My electrometer’s display has gone blank, what should I do?
- Attach the power supply to the electrometer to operate from AC power and/or to charge the battery. Ensure amber battery LED is lit or else charging will not occur. If amber battery LED remains unlit when the power supply is attached, press the pinhole reset button located on the rear of the electrometer. The electrometer should still function if used with direct AC power, even if the battery is drained or non-functional.
- If the electrometer has “locked up” or has a blank display, push the pinhole reset button on the rear of the instrument.
- If these techniques do not resolve the issue, contact Standard Imaging for assistance. Click here for contact information.
Q In general, how do I properly zero the electrometer + extension cable + ion chamber system?
Note: These instructions apply to usage with Standard Imaging electrometers. Please refer to your electrometer’s documentation for specific details.
- With nothing connected to the input jack of the electrometer and the dust cap on, turn the power on and wait for the electrometer’s designated warm up time.
- If applicable, select the desired operating range as described in the electrometer’s user manual.
- Perform a system zero as described in the electrometer’s user manual.
- Connect the ion chamber (and extension cable, if used) to the electrometer and select the desired voltage bias. Allow at least 10 minutes for the system to stabilize.
- Verify the leakage of the ion chamber is within the manufacturer’s stated acceptable limits.
- Repeat the zeroing process as in step 3, but now with the ion chamber (and extension cable, if used) connected.
Q What are the differences between the MAX 4000 and MAX 4001 Electrometers?
- The only difference between these two models is the bias configuration.
- The MAX 4000 bias options are: -300, -150, 0, 150, 300 V
- The MAX 4001 bias options are: -300, -100, 0, 100, 300 V
- The MAX 4001 was specifically designed to handle 1/3 bias ratio measurements required by the TRS-398 protocol.
Q How do I zero my electrometer?
- To zero your electrometer, press and hold the MODE/ZERO button (on older electrometers, the MODE button) for 2 seconds. To learn more about when to zero your electrometer, click here.
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