Calibration
We will calibrate any control/tube combination, including hot cathode gauges, cold cathode gauges, and low-vacuum gauges against our National Institute of Standards and Technology (NIST) standards, providing a multipoint readout and graph, in the range from 10-7 to 103 Torr. The service sets all of the available control parameters for the most accurate pressure readings, as well as establishing the functional performance of the system to a NIST-traceable standard. For more information click System Calibration.
Ideally hot-cathode ion tubes could be calibrated and characterized by their sensitivity -- that is their "gauge factor" -- without regard to the control used to operate the tube. GFV calibrates tubes using our NIST-tested controls; the gauge factors so measured can be used to establish NIST-traceable pressure measurements when the tubes are used on other "qualified" controls. For more information click Qualification.
Hot-cathode tubes from any manufacturer with any service history can be certified for use with GFV controls or qualified controls to provide NIST-traceable measurement with the same precision as new GFV tubes. For more information click Tube Calibration.
Repair and Certification
GFV continues to provide repair and certification for our IGC-1 and IGC-10 ionization gauge controls. Certification price is $250.00; delivery is one week from receipt of the control.
Question: Why calibrate my high vacuum pressure-measuring systems?
Answer: Because measuring equipment sensitivity changes. For example, using a pressure-measuring system, a process is determined to require a pressure reading of 1x10-5 Torr or less. The lower curve of the figure shows the pumpdown curve for this process; in 30 minutes the system reaches a low enough pressure and the process is initiated. After a year, the pumpdown curve shown in the upper curve of the figure is observed; now it takes 46 minutes to reach 1x10-5 Torr. The pressure-measuring system has drifted from its calibration at the time the process requirement was established. It is misinforming the operator; the system is really reaching the required pressure in 30 minutes and the operator is taking 16 minutes longer than necessary.
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Question: Can a pressure-measuring system really drift this far from an initial readings over the course of a year?
Answer: Yes; in some cases it may drift even more.
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Question: What causes pressure-measuring systems to drift?
Answer: Electronics drift in the control and sensitivity drift in the tube used. Changing the tube is a major source of calibration change. Most ionization tubes and cold cathode tubes vary in sensitivity, even when new, by a substantial amount from the manufacturer's nominal value.
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Question: How often should I have my system calibrated?
Answer: The time depends on the control used, the tube used, and the process. Only experience is a reliable guide. In the absence of experience, we recommend calibration at the time the pressure-measuring system is used to establish the process parameters, thus establishing a benchmark value. We recommend recalibration in one year or on the first indication of significant departure from the usual pumpdown time.
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Question: My pressure-measuring system is built into my equipment. Can I still have it calibrated?
Answer: Yes. We maintain a free consultation service which can provide special calibration methods for built-in systems.
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Question: I have lost the instruction manual for my pressure-measuring system. Can you still calibrate it?
Answer: Usually we can. We maintain a library of instruction manuals; if necessary, we obtain information about your control from other sources.
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Question: My control is broken. Can you fix it and then calibrate it?
Answer: We inspect all incoming controls. In cases where repair work is necessary, we supply a quotation for the cost of repair; you can decide to proceed or not.