A minimum acceptable resistance value is usually specified ( typically in the megohm ( M? ) range per circuit tested ).
12.
M? cm ( actually ? meter ) is the SI unit but some books use the term megohms per cubic centimeter.
13.
For ease of use, the doubled vowel was removed from kilohm and megohm ( instead of using kiloohm and megaohm ).
14.
Active probes are commonly seen by the circuit under test as a capacitance of 1 picofarad or less in parallel with 1 megohm resistance.
15.
For example, the 9 megohm series resistor is shunted by a 12.2 pF capacitor for a time constant of 110 microseconds.
16.
The amplifier has a very high input impedance, typically one megohm, so that it draws only a tiny current from the signal source.
17.
The upper end of multimeter measurement ranges varies considerably; measurements over perhaps 600 volts, 10 amperes, or 100 megohms may require a specialized test instrument.
18.
But in the first part of the twentieth century, electrical engineers began to use capital M for the prefix mega-, as in megawatt and megohm.
19.
Most 10?probes are equivalent to a load of about 10-15 pF and 10 megohms on the DUT, with 100?probes loading the circuit less.
20.
Probes intended for up to 100 kV typically employ a resistor voltage divider, with an input resistance of hundreds or thousands of megohms to minimize circuit loading.
