Fluke PRV240 Electronic Voltage Source/Proving unit Backgrounder
The Fluke PRV240 is simply an Electronic Voltage Source. The Fluke PRV240 proving unit provides a safe,
risk free and convenient method for verifying proper operation of your test instrument before
attempting to verify either an energized source or a de-energized source. Shock and Arc Flash protection
are no longer needed when using the PRV240 for tester verification before and after absence or
presence of voltage testing. Useful in hazardous locations or where no known voltage source is available
to verify your test tools.
NFPA70E and GS38 require users to perform an operation verification
test to verify proper operation of their test tools before and after
“absence or presence of voltage “testing is done and work can be
performed on circuit parts operating at 50 volts or more. Verification is
also required before testing or troubleshooting in live environments.
These verification tests must be performed on a “known voltage
source”. (NFPA70E article 110.4 (A) (5)). The recommended practice
would be to make these tests at similar voltages levels close to what
will be tested when live, if available.
To verify their testers, users have several alternatives to accomplish this:
1. Use a convenient electrical outlet. If one is available users would not necessarily need a Fluke
proving unit.
2. If an outlet is not available then users generally would have to remove panel covers to access
live conductors to do the verification while suited up in appropriate PPE for the specific
environment. Two issues arise from using this method for verification: First, making a live
verification test on a high energy system poses unnecessary risk for shock and arc flash for each
time a user makes contact with live conductors before and after tester verification. Potential
accidents can happen each time a worker makes contact with live conductors. Secondly,
verification on high energy panel conductors requires arc flash gear. The PPE is generally
uncomfortable depending upon the conditions and the arc flash hood face shields are heavily
tinted. This makes it hard to see or read test tool display readouts.
3. There also may be some field or remote situations where no live power exists or no easy access
exists at all for users to use as a tester verification reference but the user still needs to work
safely.
In cases 2 and 3 above using the Fluke PRV240 as secondary known voltage sources for tester
verification would eliminate the shock and arc flash risk for two of the three verification tests and also
provide the worker with an alternate test method for tester verification, especially if a known power
source is not present.
Can the Fluke PRV240 be considered a known voltage source?
Yes. The Fluke PRV240 proving unit provides a regulated and fixed ac or dc output voltage of 240 volts
specifically to allow for verification testing of Multimeters, Clampmeters or testers. Other proving units
that offer ramp type output levels or units that only source one fixed output level are not suitable for
verification testing of multimeters or digital clampmeters. Ramping units were designed and intended to
be used for verification of two pole testers or voltage testers that only used indicator lamps.
A performance verification procedure will also be available to cal labs or customers who want to verify
the accuracy of the output based upon the accuracy specifications using traceable calibration standards
or a calibrated digital multimeter that has an accuracy of at least +/- 1% of input.
Here is an excerpt from the 2015 edition of NFPA70E
NFPA70 E Article 110.4 (A)(5) Operation Verification wording change
When test instruments are used for testing the absence of voltage on conductors or circuit parts
operating at 50 volts or more, the operation of the test instrument shall be verified on a known
voltage source before and after an absence of voltage test is performed.