Source for in-line amp meter?

[Don Baer]

Dev,
$72.20 from MacMaster Carr. Do a search on there web site for Current transformers.

[Dev Emch]

Actually there is no such thing as an inline amp meter esp. when you get into higher voltages. Instead, a shunt current is monitored through a very high reistance precision resistor. In the case of an analog meter, the actual meter is a D'Arnsval movment in which the face has been calibrated to read amps based on the value of the shut resistor. In essence, anything in which you can read a voltage can be calibrated. The fuel gage in your car is based on the same principle but instead of reading volts, its calibrated to read level of gasoline based on the variable voltage measurement comming off your fuel level transducer. You can do the same thing with the planer. You can actually make up a paper face for your meter to read SHARPEN - GETTING THERE - SCARY SHARP. Install a set of dog knives and take a reading of voltage. Then adjust your sensing resistor in terms of OHMs so that the needle is at full deflection or minimal deflection (which ever your looking for) for the dull knife set. Repeat with super sharp knives. Now you have some calibration points to work from. Clearly some are wondering why I mentioned volts in place of amps. Well, if I know the voltage drop across a precision resistor of known ohms, then by OHMS LAW, I now have the amps. Volts = Resistance * Current (I). Simple and oh so cool!

[Brian Dormer]

If you decide to use the clamp on meter (known in the trade as an Amp-Clamp) - you need to be aware of something....

If you just put the clamp around the regular power cord - you will get a reading of ZERO.

You will have to construct a short extension cord that has the hot wire (usually black, the other wires should be white (neutral) and green (ground)) seperated from the other two. You put the clamp around the hot wire to measure the current load. Note that this is for 110v.

IMHO - the amp clamp is BY FAR the easiest and safest method to measure current draw on large machines. It doesn't require any cutting of wires or inserting shunts into the circuit.

Amp Clamps are widely available - I got mine on sale for less than 20 bucks at Radio Shack. Came in a nice plastic case and all...

bd

[Matt Meiser]

Harbor Freight sells a usable clamp on meter for under $20. I did some testing on mine and found it to be plenty accurrate for checking basic loads and such. It might be worthwhile to pick one up to test out the concept.

[John Weber]

Tom,

ebay is a great source. Here is a link to my post about adding a meter to my Performax drum sander.

http://www.sawmillcreek.org/showthre...ight=performax

John

[Bruce Wrenn]

Along these same lines I am thinking of getting one of these things.



It's a current tranformer with an adjustable relay. Thinking about putting it in the circuit that will feed my TS,Router etc to automatically turn on the DC when I start a tool. That and a little off time delay timer and I should be set....

It is a current sensor, probably from SSAC. Look up article on dust collector switch in FWW Aug,2000. I use this with a cube timer from Grainger to operate DC. Cube timers are available in both delay on and delay off. I use delay off as this lets DC run for about 10 seconds after shut down. This allows any dust in pipes to be cleared. By using article on efficent shop wiring in Popular Woodworking and adding a selector switch for 110 recpt. you could have either DC or no DC. Check Grainger as this sensor isn't in their cat., but they can probably get it. SSAC doesn't do direct sales, so you will have to go through one of their distributors.

[Dev Emch]

It is a current sensor, probably from SSAC. Look up article on dust collector switch in FWW Aug,2000. I use this with a cube timer from Grainger to operate DC. Cube timers are available in both delay on and delay off. I use delay off as this lets DC run for about 10 seconds after shut down. This allows any dust in pipes to be cleared. By using article on efficent shop wiring in Popular Woodworking and adding a selector switch for 110 recpt. you could have either DC or no DC. Check Grainger as this sensor isn't in their cat., but they can probably get it. SSAC doesn't do direct sales, so you will have to go through one of their distributors.

Your absolutely correct. It is SSAC which is owned by ABB. You may wish to try the various ABB distributors but McMaster Carr may be your best and most convienent source.

[lou sansone]

well ... back to the original reason for this monitor ...
I agree with tod and carl .. I just don't see the need for a planer.. wide belt yes and maybe some gigantic 50 or 75 hp planer in a large mill, but I really don't think it will show much meaningful info.
Lou