wacky DVM [RE-wrenches]

[John Berdner]

Jack,

I am not familiar with the IOTA but I think it is a switch mode charger.
The high frequency switching noise could be leaking into the meter.
The noise gets in through the meter's power leads or the voltage sense
leads (if any).

High frequency noise was a problem with some of the old APT 3 meters in
48 Vdc systems. It ended up being a power supply oscillation at > 1 Mhz
so it was really hard to find.

You could take a look for noise on the dc line with a scope or try
filtering leads to the meter. If you make one up with clip leads on all
4 wires then you can try it to see if it this solves the problem

Something like this: (ASCII Draw)

  B+ -- 10k to 100k resistor --|-- Meter sense +
                               |
                      1uF to 10uF capacitor
                               |
  B- -- 10k to 100k resistor --|-- Meter sense -

If the meter has separate dc supply and sense leads you might have to
filter both.
The input impedance of the meter sense leads should be high enough that
the resistors will not effect the accuracy of the measurement.
I don't know how much power the meter draws so you might have to
decrease the values of the resistor and increase the size of the
capacitor on the meter power leads.

Hope this helps

If you have any questions or I can be of any further assistance please
do not hesitate to contact me.

Best regards,

John Berdner

SMA-America, Inc.
20830 Red Dog Road
Grass Valley, CA  95945
Tel: 530.273.4895
Fax: 530.274.7271

----- Original Message -----
From: "Jack West, Talkeetna AE" Sent: Monday, May 28, 2001 12:51 AM
Subject: wacky DVM [RE-wrenches]


DVM works well and reads accurately until Iota comes on
> line, then reads about 3 volts high.  Problem goes away as soon as
> charger is unplugged.

- - - -
To send a message: RE-wrenches at topica.com

Archive of previous messages: http://www.topica.com/lists/RE-wrenches/

List rules & etiquette: http://www.mrsharkey.com/wrenches/etiquete.htm

Check out participant bios: www.mrsharkey.com/wrenches/index.html

Hosted by Home Power magazine

Moderator: michael.welch at homepower.com


- - - -
To send a message: RE-wrenches at topica.com

Archive of previous messages: http://www.topica.com/lists/RE-wrenches/

List rules & etiquette: http://www.mrsharkey.com/wrenches/etiquete.htm

Check out participant bios: www.mrsharkey.com/wrenches/index.html

Hosted by Home Power magazine

Moderator: michael.welch at homepower.com

==^================================================================
EASY UNSUBSCRIBE click here: http://topica.com/u/?bz8Qcs.bz9JC9
Or send an email To: RE-wrenches-unsubscribe at topica.com
This email was sent to: michael.welch at homepower.com

T O P I C A -- Register now to manage your mail!
http://www.topica.com/partner/tag02/register
==^================================================================