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6.9 Making Capacitance Measurements
Pressing []selects capacitance measurement. Measurements are made using the INPUT
HI and LO sockets within the yellow area of the panel. Five ranges (10nF to 100µF) are
available with 1200 count full scale giving resolutions of 10pF to 100nF respectively.
Zero calibration at the factory is carried out with no test leads connected; ideally, capacitors to
be measured should be connected directly to the sockets. Test leads, if used, should be kept as
short as possible to minimise stray capacitance but nevertheless a non-zero reading will
generally be present when the lowest ranges are selected. To eliminate this offset it is
recommended that the meter reading is nulled, once the required range has been selected, with
the test leads in their measurement positions but no capacitor connected.
It is also recommended that battery operation is used when making capacitance
measurements, to minimise reading jitter. Note that, because the capacitor is discharged
between each measurement, the reading rate on the 100µF range is slower.
6.10 Over Voltage Protection
When making measurements of Resistance, Capacitance, Temperature, Continuity or Diode
checks an internal protection circuit protects the current source from source voltages applied to
the INPUT HI and LO sockets. If a voltage of greater than typically 10V is applied to the INPUT
HI and LO sockets the protection circuit will be engaged, the buzzer will sound and {trIP} will be
displayed. After completion of the trip event, the measurement mode is set to Vdc to show the
over-voltage that is being applied to the input sockets. BIT 0 of the Input Trip Register (ITR) is
set to 1 (over voltage protect) see section 15.1
.
6.11 Measurement Hold
Hold operates only on the primary display. Pressing [Hold] causes the measurement to be
frozen on the display along with a {HOLD} symbol. Provided that the meter is not in dual
measurement mode and not measuring capacitance, the normal, updated, reading will be
shown in the secondary display.
Hold only operates on the primary display, any measurement being shown on the secondary
display will continue to update normally.
Hold is cancelled by pressing [Hold] again, or by changing range or function.
6.12 Measurement Null
Null operates only on the primary display. Pressing [Null] causes the measurement to be
stored and subtracted from all future readings. Pressing [Null] locks the meter in the selected
range and shows {NULL} (and {MAN}) symbols. Provided that the meter is not in dual
measurement mode and not measuring capacitance, the normal, un-nulled, reading will be
shown in the secondary display.
Null is cancel by pressing [Null] again, or by changing range or function.
6.13 The Cancel Key
[Cancel] can be used to return the meter to a basic measurement mode. It cancels dual
measurement mode, dB, Null, Hold and T-Hold, and any programmable functions including the
Logger. It does not cancel : Null.
Consequently [Cancel] should not be used to cancel a single function, such as Hold, if other
functions need to be maintained.
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