10
Trouble-shooting
In order for your DPM system to function properly, the meter, the reference electrode and the test leads must
all be in satisfactory condition. The following are some simple tests that you can make to isolate any apparent
source of trouble.
If there is no display in the window when 2V or both 2V and 20V range buttons are pressed, open up
the meter (see section on battery replacement) and check to see that the battery is in place. If properly
connected, it is held in place by the spring retaining clip. Also check to make sure that if nothing
appears to be wrong, replace battery. If this does not cure the problem, check for loose or broken wires
or connectors. If you cannot locate and fix the problem, send the meter back to the factory for repairs
(obtain RMA from M. C. Miller).
If the display shows all zeros or nearly so when you would expect a substantial reading, connect any
new 1.5V battery cell between the two input terminals, using two test leads and the threaded adapter.
Pressing the 2V range button should yield a reading between 1.5V and 1.6V if meter is working
satisfactorily. If the battery and the test leads are known to be OK, then check inside meter for a loose
or disconnected wire. If none of these tests disclose the problem, send the meter back for repair (obtain
RMA number from M. C. Miller Co.)
If the meter and battery appear to be working properly but readings are zero or almost zero, check
reference electrode to make sure that fluid inside the electrode is contacting the copper rod and that the
orange plastic cap has been removed from the bottom of the electrode tube so that the moist porous
plug can contact the soil (or water) properly. Also check to see that there are some excess un-dissolved
copper sulfate crystals in the electrode tube.
If the meter, battery and electrode appear to be normal but the reading is not obtained or is intermittent,
check test lead using an ohmmeter or substitute another test lead.
Zero or lower than anticipated readings are sometimes caused by frozen soil, dry sand, rock
or paving being in contact with reference electrode. Try using a cup of tap water on point of
contact of porous plug to lower contact resistance. Freezing of electrode fluid will produce the
same problem and destroy the electrode. Use of MCM’s Electrode Anti-Freeze Solution will
permit the electrode to be used or stored down to about -10F without damage. Avoid taking
readings through paving material whenever possible.
Intermittent jumpy readings can be result of using the meter too close to a transmitting antenna of a
mobile radio system. The only practical solution is to either move further away from the antenna or to
not key the transmitter when attempting to take readings.
Precautions
COPPER SULFATE
, which is the main ingredient inside your reference electrode, is listed as a toxic
substance. It must NOT be ingested and body parts should be washed with water if contact is made with
either copper sulfate or the electrode solution. Keep copper sulfate and reference electrode away from
children. Please consult the Copper Sulfate Pentahydrate Materials Safety Data Sheet (MSDS) supplied
with your DPM Kit for proper handling instructions.
