Seaward DO4000 - Manual (Page 15)

Operating Instructions Digital Ohmmeter DO4000 Series
13
10. Power Up
When the 4000 series is first switched on, a lamp test is automatically performed,
all display segments are illuminated. The microprocessor checks for correct
internal operation and indicates "P" if all tests pass OK At the same time the
software version will be displayed and held for approximately 2 seconds. The
display will typically read "P 1". Should the internal checks indicate an error, then
the display will read "FAIL". The unit should be returned to Cropico or its agent for
rectification if this error message appears.
The 4000 series will perform an automatic zero sequence and finally sets to the
following default start up mode ready for use. The measuring range 4K
Ω selected
manual range mode with +I current mode selected.
Automatic Power off To ensure the maximum battery life, the DO4000 series will
automatically switch off after 10 minutes if no keys are pressed.
11. Measurement
Connect the resistance to be measured (Rx) to the measuring terminals in
accordance with the diagram on the instrument panel. Select the range required.
The LEDs to the right of the display will indicate the units m
Ω, Ω or kΩ.
Auto Zero this function will zero any thermal emf within the measurement circuit.
Connect to the Rx to be measured in the normal way, select the required
measurement range and press ZERO. The current leads are shorted internally and
any emf present in the Rx circuit measured by the potential leads (U and U1). The
4000 series will then set the display to zero cancelling out this emf.
This function is suitable for use on inductive circuits and will be cancelled if
another range is selected or the ZERO key is pressed again.
If during measurement, any of the error messages should be displayed, then
obviously the appropriate action should be taken.
Whilst the input is protected against accidental application of mains voltage,
single or 3-phase, care should be taken to avoid measuring on live circuits.
Over-range The display will indicate - - - -.
Open Circuit Lead OC will be displayed if the instrument detects that the lead
resistance is too high. The + and -I terminals are checked for compliance voltage.
This warning will also be displayed if the internal protection fuse is open circuit.
Connections When making good quality measurements, it is important to ensure
that all measuring leads are in good condition, and less than 0.2 ohms resistance.
It should also be noted that some spade tags and crocodile clips can produce
high thermal emfs when warmed, particularly nickel-plated brass types. This can
cause problems when, for example, connecting too hot motor windings. The
solution is to use plain copper or brass connections keeping them clean and oxide
free.