5735 Currrent Meter - NO Manual

[Kpaxman]

Hi Marco,

I've attached a pdf drawing of my application along with my recent order information.
I didn't see a drawing or any application sheets for the 5735 in the boxes that came or on the forum manual download section. The designation points on the plastic housing are a little cryptic, for instance - V + .... I had to look at the circuit to tell this is the DC in because its connected to the DC to DC converter. Then the + IN - must be for the AC? right? However it shows polarity +/- strange ...... then its shorted together on the (PCB). So is this a probe point? It doesn't carry any of the load??? Because it only has a 20 ga. jumper which isn't nearly large enough to sustain a constant 18Amp load. Please get back to me ASAP so I can move this project forward.

Thanks,
Jeff Burns

> From: [email protected]
> To: [email protected]
> Subject: Annex Depot Inc. Customer Receipt/Purchase Confirmation
> Date: Fri, 19 Mar 2010 15:55:21 -0600
> ========= GENERAL INFORMATION =========
>
> Merchant : Annex Depot Inc.
> Date/Time : 19-Mar-2010 02:55:21 PM
> Transaction ID : 2900086145
>
> ========= ORDER INFORMATION =========
> Invoice Number : 182948
> Description : Lightobject Order #182948

[Tech_Marco]

The +/- input seems short but it's not. It's a dc type shunt. Just put the input in series to your load and it will read proprly.

[Kpaxman]

Marco,

That tiny wire is a DC shunt.....? I know your sure, I'm being sarcastic.

I'm not sure if I can go to my boss and tell him that his POWER DISTRO for the AMPS which provides sound to a crowd of over 5,000 people at an average concert.... All rides on that tiny shunt.

Did you see the specs on the pdf, I included (items 2 - 4 ).
The distro uses 20 Amp breakers and 10ga. wire.

I know I mentioned the other current meters I had purchased from China, when we were on the phone. Although they stopped working properly....most likely not having isolated DC to DC converters. However they used a beefy 50AMP/75mV shunt. So the show went on without a major problem.

I have a fully equiped electronics shop, with seven componet level techs on staff. Can't I just change the load resistors R1,R3 and pot and recalibrate theses things...using the 50A/75mV shunts I have... or... I even have inductive tranformer chokes we use on another current sensing systems we make for the golf industry. They are a 20:1 and we use them on 24vac system, but they would most likely work as long as I again change the load resistors and pot and recalibrate. ???? YES ????

I really don't want to return the 5735's, because I couldn't see this potential problem before I purchased them. I'm sure we can figure this thing out and save each other alot of time and grief.

Thanks again,
Jeff

[Tech_Marco]

Why don't you just try it and see if it blow. Or, have you seem a fuse of 30A as big as a #10 guage wire?. Remmeber, distance is an issue and the materials that make that 'little shunt' is different. It's a specail alloy. Just hook up a heater of something that draw 30A and test the meter for 20~30 min, if it's no good, it blow right there. Current breaker is a different animal. I don't want to wast time on this subject if you don't try it. I'm currently out of country and very busy. I don't want you to waste your time either, simply send it back for refund if you don't believe it works

[Kpaxman]

Marco,

That sounds like a reasonable request. I'll test it. I know you believe in your product. And yes, you are right, different alloys make all the difference, If it weren't so an average TO-3 op-amp can with the similar 20ga material would blow with similar load....."They don't". Enough said. I to travel over sea's all the time, so stay safe and make the most of your travels. I'll post regardless of results for the forums benefit. I hope it is a win win for both of us.

Thanks,
Jeff

[Tech_Marco]

Jeff:

I fogot to mention, if it blew, I'll give you a FULL Refund. Sound good to give it a try now ?!

Marco
(in China now)

[Kpaxman]

Project requirements: Add a current meter to a power distribution, that will draw 18 amps continuously through (2) 20 amp breaker 120V circuits with a MAX load of 24 amps through both.

5735 current meter Test and results as follows:

DC power supply 12V/wired 18ga. copper stranded.
AC 120V/wired 12ga. copper solid Romex type house wire. This would seem to be about the maximum size. That will fit in the terminal connector.

Initial test was made using a small vacuum with a current draw of approx. 6.5 amps. The (TENMA) commercial inductive current meter I was using displayed a reading approx. 0.5 amp more than the 5735.

3 - 5 seconds after switching the unit on a slight discharge of smoke was emitted from the shunt on the 5735. Then I noticed the 5735 display began to dip slightly over the net few minutes 0.3 amps. We are now 3 minutes into the test since I first activated the circuit.


At this point I added a 2nd vacuum which increased the current draw to 11.7 amps. Again there is a slight discharge of smoke similar to a typical burn in cycle for a soldering iron heating element. The shunt now shows signs of discoloration like that of tempered metal. We are now 6 minutes into the test since I first activated the circuit.

Next I added an adjustable temperature heat shrink gun. At the low setting the 5735 displays a current draw of 16.5 amps. I thought I would check to see how hot the shunt is getting and weather the solder holding it in the through hole was still solid. So I rolled a small piece of paper towel about the size of a toothpick to press against the shunt. It immediately started to smoke however the shunt seemed to still be held in the through hole solidly. We are now 10 minutes into the test since I first activated the circuit.

I momentarily switched the shrink gun to hi which immediately showed an ERROR on the 5735. This I suppose is correct if the current draw exceeds the 20 amp specifications.

Switching the heat shrink gun to the medium setting now displays 18.2 amps. Once again I test the shunt with the rolled paper towel. Again the paper smokes, however now the shunt is just sloshing about in liquid solder, and if it weren’t for the “U-bend” in the shunt it would fall out of the PCB. We are now 12 minutes into the test since I first activated the circuit. I concluded the test 15 minutes after I first activated the circuit.

Summary:
It is apparent that the shunt is still holding its own at this point and hasn’t failed. However the circuit has been compromised with the solidification of the solder at the base of the shunt. With more than 22 years experience as both an electronic technician and engineer. I would think any sustain current above 10 amps (HEAT BUILD UP) would eventual compromise both the PCB and the plastic housing that sets relatively close in proximity to the shunt. I see no way to dissipate the heat resonating from the shunt. I later went back and dropped the current to see what might be sustainable, and 8 amps will still melt the plastic on my tweaker if pressed, but may be sustainable, if the project is tight on space. My project has plenty of room for an external shunt. So I'm going to check that out next.

Further Testing:
I went on to modify the circuit. I removed the tiny internal shunt on the 5735 PCB and installed an external 50A/75mV shunt (physical size is approx. 4” x 1”) similar to that sold at lightobject.com. I then made a couple of component mods then recalibrated and retested the circuit drawing 18.2 amps continuously. The unit performed flawlessly and the shunt and 5735 circuit remained cool to the touch. I concluded this test after 5 HOURS of activation.