Harbor Freight Meter Modification
On a recent visit to Harbor Freight I discovered
that their small volt ohm meters were on sale for $1.99!
|Some time ago I took two of the Harbor Freight meters, which
cost nearly $5.00 at that time, and put them on a board wired so
that one would continually show voltage readings while the other
This worked well and it comes in handy when testing circuits and engines.
Here is the wiring diagram for the above setup.
|I like the above setup but wondered about modifying a single
meter so that it could be easily and quickly switched between
showing voltage and current.
This is normally something of a chore as voltage is measured by putting the meter in parallel with the load on the circuit as in the diagram below.
Measuring current requires that the circuit be broken and the meter inserted in series with the load.
I surmised that I would have to add a switch to make the change between measuring voltage and measuring amperage.
|After a bit of experimenting I made an interesting discovery.
If you wire the meter as in this diagram you can measure voltage by
putting the selector in the DC volts range and current by moving it
to the 10 Amps range. No other switching is needed!
This works because you are always routing the power to the motor through the shunt that connects the command and 10 amp plug. I have moved the selector through the full set of ranges and have noted no damage to the meter.
Give it a try and see what you find with your meter. No guarantee that it won't cook your $500.00 Fluke but it sure works well with my $2.00 Harbor Freight!