Fluke 87V-MAX Product Manual - Page 28

When measuring resistance, be sure that the contact between the probes and the circuit under test is good. Dirt, oil, solder flux, or other foreign matter seriously affects resistance. Most in-circuit resistance measurements can be made without removing diodes and transistors from the circuit. The full-scale measurement voltage produced on ranges below 40 MΩ does not forward-bias silicon diodes or transistor junctions enough to cause them to conduct. Use the highest range you can (except 40 MΩ) to minimize the possibility of turning on diodes or transistor junctions. Fullscale measurement voltage in the 40-MΩ range does forward-bias a diode or transistor enough to cause it to conduct. In resistance (and all other functions except current), the mA µA input is connected to a 1-kΩ resistor. If the mA µA input protection fuse is good, this input can be used as a partial check of proper operation in resistance. The input receptacles have split contacts; touch the probe to the half nearest the LCD. The 1-kΩ resistor is protected by a 3diode clamp. Do not apply external voltage; it may blow the fuse. Applications Using Conductance for High Resistance or Leakage Tests Conductance is the inverse of resistance (i.e., 1/ohms) and is measured in units of nanosiemens (nS = 1 x 10-9 Siemens). The 40-nS range on your meter effectively extends the resistance measurement capability to 100,000 MΩ. The 40-nS range can, therefore, be used to test the resistance or leakage in insulators, diodes, transistors, cables, connectors, printed circuit boards, transformers, K motors, capacitors, or other high resistance components. To measure conductance, set the rotary switch to MJ and press Kto manually increment to the 40-nS range. Plug the test leads into the VJL and COM input terminals, and then connect these leads across the unit under test. The reading displayed is in units of conductance (nS). To convert this reading to megohms, divide the reading into 1000 (1000/displayed reading in nS = MΩ). For example 2.00 nS converts to 500 MΩ (1000/2.00). High value resistance measurements are susceptible to induced noise and may require careful shielding. To smooth out most noisy readings, enter the MIN MAX Recording mode and scroll to the average (AVG) reading. 21 MyFlukeStore Find QuaSlhitoypPforordFulucktespOrondliuncetsato:nline awt:ww.wGwlo. balTestSupply.com.com [email protected]