Warning messages:
'Contact Limit' means that you should try reducing the current or improving the
contact on the sample.
'Out of Range' means that you are exceeding the voltage input of the DVM, reduce
the current or try Low sensitivity if the current is already at its minimum.
'Battery Low' means the unit needs to be charged. It is detected when changing to
Standby and will occur first during reverse or at higher currents.
The unit is designed to charge the batteries with a trickle charge to give long life so
recharge time can be up to 48 hours. However fully charged you can expect a very
long usage time - if used continuously charging will only be required every week or
two. With occasional or light usage several months operation is possible. The unit
can be operated while connected to the mains at any time whether batteries are
present in the unit or not. The USB charge feature can be used to keep the unit
topped up but can't be used to charge the unit when the batteries are very low. The
batteries must always be rechargeable AA Nickel Metal Hydride or similar type.
The unit will completely turn off after 30 minutes if left in the Standby mode. The
unit can also be switched off using the On/Off button - it should be noted that the
On/Off button need only be pressed once to turn the unit off - there may be several
seconds delay before the unit closes down.
Measurement range is:
1 ohm/square to 10 Megohms/square (in practice you can measure down to around
0.01 ohms/square but the accuracy may be compromised slightly)
This equates to a range of approx. 0.01 ohm.cm to 100 Kohm.cm
Remote control is available via USB.
Command is via simple single character commands. Data Output data is in the form
of comma separated variables (CSV). Sending an "o" to the HM21 causes it to
Send or Output the set Current and the Voltage Reading displayed at that time.
The USB Port utilizes an FTDI device, and drivers are available on the web site:
http://www.ftdichip.com/ or
http://www.ftdichip.com/FTDrivers.htm (FT232BM)
