Analysis of Voltage Measurements and Resistance In Inverting Amplifier |
Currentmeasurements are made on one of two ways. The first and most straightforwardmethod is the reverse of the Resistance measurement. In this configuration, theunknown current is applied thru a known, but very small, resistance, and theresulting voltage is measured. Many hand held multi-meters will measurecurrents of up to 10 Amps. Frequently a second resistance value for currentwill be available that is larger, allowing much smaller currents to be measuredaccurately. The second method utilizes field effect properties of currents flowingthru conductors. By wrapping a coil of wire around the wire, the field effectsof the current flow thru the wire will induce a current in the coil. In thisway the current can be measured without the resistance being installed. Thismethod is typically used for higher current flows and can be used for readingsin the thousands of amps. Most hand held multi-meters that measure current willhave a special input jack for the positive lead of the current measurement.Failure to change to this location can cause considerable damage to themulti-meter, since the total current flow would be trying to go thru thevoltage measuring circuit.