|Marconi Instruments TF868/1
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|Another superbly built
piece of kit from the stable of Marconi Instruments -
purveyors of fine laboratory grade receivers,
transmitters and test gear to Governments everywhere.
This device is easily outperformed these days by any
cheap DMM - except with a great deal more panache! It is a direct reading instrument which
measures values of inductance from 1µH to 100 Henrys,
capacitance from 1 µµF to 100 µF, and resistance from
0.1 Ohms to 100 Megohms.
The instrument uses the large, single dial for the measurement of inductance, capacitance, and resistance values. Changing the setting of the LCR and RANGE selector switches automatically changes the dial calibration together with the bridge circuit conditions to suit the component under test.
For inductance and capacitance
measurements, an RC oscillator-amplifier (switchable to
either 1 Kc/s or 10 Kc/s) supplies the voltage. The out
of-balance bridge voltage, after amplification and
detection, is displayed by the centre-zero meter on the
front panel. Measurement of L or C is normally made at 1Kc/s;
however, the use of 10 Kc/s is advantageous, for example,
when evaluating low-Q inductors.
The 'Phase Balance' control is used
to balance out out the resistive component when
inductance and capacitance are being measured. This
control has two scales which are calibrated in 'Q' and
'Tan' - the appropriate scale being selected by the Q-Tan
switch. The Q scale is calibrated from 0.1 to 10, and the
Tan scale from 0.001 to 0.1. Q is normally used for
inductors and Tan for capacitors.
The test terminals are located on top of the instrument; the flat top provides a useful insulated platform for supporting the component to be tested. This also has printed basic instructions for the device's use
Last updated 4th September 2003