Lionel 6-14002 ZW amp/Volt Meter

Different volt meters respond to different values of the
input signal. AC volt meters are calibrated to indicate the
RMS value of an input sine wave.The old ZW output was a sine wave
so the amp/volt meter was calibrated to indicate a sine wave input.
The output of the new ZW is not a sine wave but a clipped
sine wave so the meter is calibrated to indicate the RMS value of
a clipped sine wave.

If you use a meter calibrated for the new ZW on an old ZW,the reading will be
different than a neter caliberated for a sine wave input.The error is not that much.

Thank you.
So I could get it and probably there might be an internal adjustment pot I can tweek. If none not big deal.

I wired one to my KW and it worked great. I also had two circuits of my V hooked up to keep track of accessory voltage.
John

quote:

Originally posted by pa:
Different volt meters respond to different values of the
input signal. AC volt meters are calibrated to indicate the
RMS value of an input sine wave.The old ZW output was a sine wave
so the amp/volt meter was calibrated to indicate a sine wave input.
The output of the new ZW is not a sine wave but a clipped
sine wave so the meter is calibrated to indicate the RMS value of
a clipped sine wave.

If you use a meter calibrated for the new ZW on an old ZW,the reading will be
different than a neter caliberated for a sine wave input.The error is not that much.

I doubt that the new one does true rms. Mine is pretty inaccurate until it gets to full output.

Aren't there two versions of that meter - one for old ZWs, and one for new ZWs?

Be advised that the amp readings are generally not correct if you have a Common bus for your layout. I have engineered a modification that will overcome this problem

quote:

Originally posted by Dale Manquen:
Aren't there two versions of that meter - one for old ZWs, and one for new ZWs?

Be advised that the amp readings are generally not correct if you have a Common bus for your layout. I have engineered a modification that will overcome this problem

I meant the volts. I assume that neither meter is true rms on either reading. But on extreme sharks tooth, where the peak is already showing, the newest one on volts is not accurate but not as far off as it should be considering. I assume the old ZW version is purely peak reading and set to .707 of peak.
Interesting about the current, I knew that, but would be interested in knowing the solution.

quote:

Originally posted by Dale Manquen:
Aren't there two versions of that meter - one for old ZWs, and one for new ZWs?

Be advised that the amp readings are generally not correct if you have a Common bus for your layout. I have engineered a modification that will overcome this problem

I thought postwar ZW used a common ground strap for all four common lugs. Current would be monitored through the hot A,B,C,D lugs. THe modern powerpack ZW must have individual commons, reqiring a different meter circuitry which a layout common ground defeats?

You will find additional technical information and a PCB photo on my trainfacts.com website.

quote:

Originally posted by Dale Manquen:
You will find additional technical information and a PCB photo on my trainfacts.com website.

Dale, how did you add the tranformers and how were they connected to the PCB circuitry?

quote:

Dale, how did you add the tranformers and how were they connected to the PCB circuitry?

With considerable care after numerous experiments.

I don't want to be responsible for anyone messing up their ZW boards.

The current transformers become little floating voltage sources. I made mine adjustable by putting a potentiometer across the output of the current transformer. The 4 inputs of the LM324 are the 4 current-sampling voltages. The transformer voltages are substituted for the sense resistor voltages.

To calibrate the sensitivity, I used an adjacent power channel to drive the current sense transformer. That way I got a sense resistor readout on one channel while simultaneously getting a current transformer readout on the other channel. I adjusted the transformer's pot to match readings.

Enough hints?

(Full disclosure: I developed and tested this technique on a customer's meter assembly for a PW ZW, but I did not permanently implement it on his unit. I do not own a ZW meter, but maybe someday I will find one. Without this modification, I consider the meter to be a lame duck.)

John H and others - I have a modern ZW with 4 180 watt bricks and want to purchase the AMP/Volt meter BUT not connect it to the actual transformer.  Is this possible?  If anyone has done this a picture may be worth a 1000 words.  My thinking is I could connect it right to my terminal blocks.

I don't have a close-up, but I did exactly this on the 2010 Christmas layout monitoring outputs of a KW. two PM-1's, and a MW(4690).  The panel can be seen in this video:

 

Rob, Thanks!  My local hobby shop has these in stock and I may pick one up this weekend.  

If you can get a twofer, send one to Dale for more experimentation and a permanent solution for its drawbacks!

I connect my meters to the main railpower distribution terminal strip shown in bottom photo. Monitoring 180 PoHo VAC.

 

 

 

 

Rob, I obtained some samples of Hall Effect current transformers that should work well in this application, but I never got around to trying them.