Rf Output Power Testing - ConMed Hyfrecator 2000 Service Manual

2000
These tests are performed most conveniently using any good-quality biomedical electrical safety tester. If
you do not possess such a tester, then it is possible to construct your own using a millivoltmeter and a simple
RC network constructed according to IEC 60601-1, Clause 19.4 e).
NOTE: There should be at least a 3-to-1 difference in measured leakage current between
the SFC and NC (earth open and connected). Absence of a noticeable change indicates a
possible open circuit fault in the mains cord or the earth-reference capacitor in the
RETURN circuit on the A2 PWB. See Section 4.4.8.

4.2.5 RF Output Power Testing

These tests verify that the Hyfrecator® 2000 is able to deliver RF output power as indicated on the power
display with specified accuracy.
NOTE: RF power measurements are difficult to achieve with accuracies better than 5%. Thus, it is quite
possible to find output power errors which exceed the specified 10% tolerance if a different instrument is
used to check power from that used to calibrate the unit. Therefore, it is advisable to use the same
instrument for both calibration and later output testing. However, output errors of less than 20% are
generally not clinically noticeable.
RF power measurements are best made using a commercial, recently calibrated electrosurgical unit (ESU)
tester having both 500 and 1000 ohm test loads.
Alternatively, a commercial 500-ohm-only tester can be used with an external series 500-ohm 20 W
(minimum) non-inductive resistor In this case, power readings should be doubled, since the tester is
receiving only half of the output power.
An acceptable tester may be constructed using non-inductive power resistors and thermocouple RF
ammeters (150, 250 and 500 mA full scale). Alternately, a broadband (10 kHz to 5 MHz) current probe
with a true-RMS high-frequency AC voltmeter with specified accuracy to at least 5 MHz may be used.
Power (P) in watts may be calculated from measured output current using the formula:
P = I R
2
where I = RMS output current (Amperes) to the load resistance R (Ohms). Acceptable output currents
according to Hyfrecator® 2000 specifications as of the time this manual was last edited have been calculated
in the table below.
Procedure:
1. Using well-insulated test leads, connect the ESU tester Plate or Return input and Active input to the
Hyfrecator® output jacks indicated in the table below.
2. Set the tester to read output power and select the indicated test load. Set the Hyfrecator® to the
indicated mode and power setting.
3. Activate the unit using a handpiece or footswitch. Allow the reading to settle for about 2 seconds before
recording the test results.
4. Compare your reading to the limits shown.
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