Making Continuity and Diode Checks
Continuity and diode checks are made using the V/Ω and COM sockets.
Pressing the Continuity/Diode check key selects Continuity mode with the first press; the
continuity indicator is shown in the display. The 1000Ω range is selected and readings below
approximately 10Ω sound the continuity buzzer.
A further press selects diode check; the diode annunciator is shown in the display. The 1000mV
range is selected and the approximate diode voltage at 0.5mA is shown (1.2V maximum).
Reverse diode connection will show overload.
Further presses of the key will alternate between Continuity and Diode check.
Making Capacitance Measurements
Capacitance measurements are made using the V/Ω and COM sockets. Capacitance
measurement is selected by pressing the µF key. 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 require 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.
Making Frequency Measurements
Frequency measurements are made using the V/Ω and COM sockets.
Press the Hz key to select frequency mode. Four ranges (100Hz to 100kHz) are available giving
resolutions of 10mHz to 10Hz respectively over an operating frequency range of 10Hz to 120kHz.
Reciprocal counting techniques ensure fast reading updates (4 readings/second) even on the
lowest range.
Measurements are made using the ac Volts input circuitry which is autoranged to provide suitable
sensitivity. At low signal levels use a screened lead and an adaptor (BNC to 4mm plugs, 19mm
pitch) to preserve signal quality and avoid spurious readings from stray pick-up. The minimum
measurable signal is typically <30mV rms across the frequency range.
Frequency can also be measured in dual measurement mode, see next section. When measuring
the frequency of an ac current the minimum measurable signal is typically <10% of range
maximum, e.g. <0.1mA on the 1mA range.
Zero Calibration
An automatic zero calibration of the basic DC measurement circuitry is performed every time that
the instrument is switched on. However, if the meter has been stored at a temperature outside
the specified operating range, and is switched on before it has fully acclimatised to the working
environment, accuracy may be affected as the meter’s temperature changes. To ensure optimum
accuracy, particularly on the 100mV and mA current ranges, zero calibration can be repeated
when the meter has acclimatised by using the Null key as follows:
Press the Null key and continue to hold it down until nULL shows in the main display (about 3
seconds later). nULL continues to show whilst the auto-zero is being performed (typically 5
seconds); on completion the display returns to it previous mode.
Auto-zeroing in this way cancels Null if this was already selected; press Null again to re-select if
required.
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