The PrimeTest 100 has some interesting features.

The abbreviations on the screen are as follows:

• “Rpe” stands for Resistance of Protective Earth and is measured in Ohms.
• “Riso” stands for Resistance of Insulation and is measured in MegOhms.
• “Ileak” stands for Touch or Leakage Current and is measured in milliamps.

The Primetest 100 can also be used to test the mains socket.
After switching the PA Tester on by holding down both the class I and class II test buttons until you hear the second “Beep”, you plug the short red IEC lead into the tester IEC socket on the top of the unit and 13Amp plug end into the mains socket. If the test is a pass, the letters LN, LE. And NE will be displayed down the left hand side of the screen each with a tick and the word “PASS” will be displayed centre bottom. If there is a fault condition, for example a disconnected earth, the LN will be displayed with a tick indicating that line and neutral are good but both LE and NE will be displayed with a cross indicating an earth failure while FAIL will be displayed centre bottom of the screen.

The PT100 sometimes displays ‘LO LOAd’ on the screen. This is usually displayed just before the Insulation test. The tester checks the load (Watts) presented by the equipment which is being tested but it can’t read below about 200 Watts. If the Wattage of the equipment is below this level, for example a 23 Watt battery charger, the LO LOAd will be displayed; it is not a fault condition, it is only indicating that it can’t see a load. You simply press the selected button again and the tester will continue with the test. The usual cause for this display is that you may not have switched the equipment on in which case switch it on and press the button again.

When testing computers the PT may fail the computer on the leakage test. This is due to the tester having ‘Fixed limits’; where there are two limits the tester will test to the lower limit. Table 15.3 on page 77 of the IEE Code of Practice 3rd edition indicates that Portable or Hand Held class I appliances should not exceed 0.75 mAmps while IT, Movable and Stationary class I appliances should not exceed 3.5 mAmps; the PT100 is set to the lower limit of 0.75. For IT, Movable and Stationary class I appliances as long as the reading does not exceed 3.5 mAmps you can pass the appliance on the leakage test even though the tester indicates a fail because it is within prescribed limits.

When you are testing long leads the PT100 may fail the lead. This is because the extra length is increasing the earth resistance to a point where it exceeds the 0.2 Ohm fixed limit. Table 15.1 on page 74 of the IEE Code of Practice 3rd edition gives the limit for IEC and extension leads as 0.1 Ohms plus the resistance of the cable. You can work this out using table VII.1 on page 124 of the C of P where it lists cable sizes and the resistance per metre and as long as the tester reading is within the calculated limit, you can pass the test.

Written By Austin