Completed Project Does anyone know how to connect and take readings from this digital panel?

Thread Starter

Rahulk70

Joined Dec 16, 2016
504
Hi,

I have received three digital precision panel meters (think its vintage by its looks), one is a Precision Instruments PD710CJ 310 and the other two Western Digital Meters. I plan to use the Precision Instruments Digital meter now, but when I googled there seems to be no data sheet on connection info on this device.

I plan to use this as this one as it has only two 115VAC terminals and there are three connection terminals only presumably for data I think (unknown configuration).
Thanks.
 

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GopherT

Joined Nov 23, 2012
8,012
Hi,

I have received three digital precision panel meters (think its vintage by its looks), one is a Precision Instruments PD710CJ 310 and the other two Western Digital Meters. I plan to use the Precision Instruments Digital meter now, but when I googled there seems to be no data sheet on connection info on this device.

I plan to use this as this one as it has only two 115VAC terminals and there are three connection terminals only presumably for data I think (unknown configuration).
Thanks.
To get readings, you place this one in the trash can and order a safe, modern one. This one has a non-standard AC connection that can get someone killed if they try lifting/moving the device when it is plugged in.

AC connectors should be recessed with no chance of contacting a user. A modern, safe replacement with similar capabilities is much cheaper than the gas money your spouse will spend to go pick out a casket.
 

Thread Starter

Rahulk70

Joined Dec 16, 2016
504
To get readings, you place this one in the trash can and order a safe, modern one. This one has a non-standard AC connection that can get someone killed if they try lifting/moving the device when it is plugged in.

AC connectors should be recessed with no chance of contacting a user. A modern, safe replacement with similar capabilities is much cheaper than the gas money your spouse will spend to go pick out a casket.
:rolleyes:Of course mate I'm not going to plug it into my wall outlet and going to get killed. I was just curious how it was used. What the connections might me? If its possible first power it with a simple 12VDC to 110V AC inverter and then see how it works. Just curious thats all.

I was hoping maybe any of our senior members might have come across this as its quite old.
 

Thread Starter

Rahulk70

Joined Dec 16, 2016
504
I was thinking of that too. But in the mean time I had an idea. I tried opening it and tried to figure it from the circuit by tracing the lines. Luckily it doesn't have a dozen pins like the other ones. The other two digital display instruments operate on 20V and 2V as the label says.

I tried powering it according to the figure and it gave a value of "1270" on the display, but the C label next to the display gave me an idea. Connected the thermocouple I had received with my multi-meter and yes I got temperature readings. Thanks for all the suggestions @GopherT.DSC_0028 edited.jpg
 
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Reloadron

Joined Jan 15, 2015
5,499
I agree with Gopher. Also if you look at the rear input connector the little device with three legs looks to be a transistor used for CJC (Cold Junction Compensation) where the base and collector are tied together. Also sometimes a part number can be a little revealing, PD710 CJ 3 N and my guess is as Gopher pointed out the display is Degrees C and the J would be a type J thermocouple. That being just a guess.

Ron
 

strantor

Joined Oct 3, 2010
5,288
That thing plugs in a rack you cant get to the power after it's plugged in.
They use them a lot to read pipe temp.
+1
modern panel meters would be just as dangerous if used outside a panel. They don't use spade terminals but they do use screw terminals. Just as exposed, same concept.
 

be80be

Joined Jul 5, 2008
2,044
I had maybe 100 of them old meters like that I used some of the displays had to get rid of the gunk when I moved here. My bedroom to small to keep it in. LOl
But there common on pipes and stuff that you need to see the temp and even some read the voltage
Just used what you needed to keep a eye on. some even real smart they showed you and talked to the computer that ran the place.
 

Thread Starter

Rahulk70

Joined Dec 16, 2016
504
That thing plugs in a rack you cant get to the power after it's plugged in.
They use them a lot to read pipe temp.
Hi,
Yes, it belonged to part of some obsolete equipment. I got a few of these and some SCR based controls etc.
But the measurement on these when connected to the thermocouple isn't accurate. Like when room temperature is around 82.4F(28C) the instrument reads like 5C less like 23C. Looks like I need to figure out how to use the third terminal A(adjust) to compensate.
 
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Thread Starter

Rahulk70

Joined Dec 16, 2016
504
+1
modern panel meters would be just as dangerous if used outside a panel. They don't use spade terminals but they do use screw terminals. Just as exposed, same concept.
The newer versions have some kind of special connectors or something like that where they go straight into the rack without the user having to deal with the high voltage sides.
 

GopherT

Joined Nov 23, 2012
8,012
The slider switch selects RTD vs Thermocouple input. I'm not sure the "A" screw is doing anything in thermocouple mode.

Here is the connection diagram for a more modern meter display. The RTD input can use two, three or four terminals. The thermocouple uses two terminals. The slider switch must be moved to TC mode.

437A1513-48BA-40B9-8645-035291F769EE.png
 

Thread Starter

Rahulk70

Joined Dec 16, 2016
504
The slider switch selects RTD vs Thermocouple input. I'm not sure the "A" screw is doing anything in thermocouple mode.

Here is the connection diagram for a more modern meter display. The RTD input can use two, three or four terminals. The thermocouple uses two terminals. The slider switch must be moved to TC mode.

View attachment 139115
Hi,
The switch close to the 3 terminals is a temp C or F selector switch. I tried opening it and it has another switch inside, but not sure if its what you meant.

There re two POTs on two sides of the display which says "Hi" and "Lo". Also I notices now that the display has another segment which has +/- too.IMG_1049.jpgIMG_1050.jpg
 
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Thread Starter

Rahulk70

Joined Dec 16, 2016
504
..? I'm out of ideas.
Sorry, an update:
1 isn't power switch, just tested keeping the circuit board outside. 1 is C or F degree selector. 2 switch is to lock the current value of temperature. I was able to adjust the temperature aka correct it using the Lo pot.
 

Thread Starter

Rahulk70

Joined Dec 16, 2016
504
There seems to be a problem though, as the device is powered down and turned back ON it starts at -18C and then keeps increasing gradually to 18C to 21C which is close to room temperature ( 23C in my case). There seems to be an error always, so it needs some kind of correction if powered down. Doesn't seem to be stable.

Maybe its something like be80be mentioned, its meant to be used at higher temps only.
 

ebeowulf17

Joined Aug 12, 2014
3,274
There seems to be a problem though, as the device is powered down and turned back ON it starts at -18C and then keeps increasing gradually to 18C to 21C which is close to room temperature ( 23C in my case). There seems to be an error always, so it needs some kind of correction if powered down. Doesn't seem to be stable.

Maybe its something like be80be mentioned, its meant to be used at higher temps only.
Are you using the right thermocouple type? Free ones with meters are often K, and someone above suggested you probably need J. I don't know either way, but it's worth making sure you've matched types.

As for the creeping temp. on power cycles, I wonder if it has anything to do with the cold junction reference circuit. The thermocouple technically only measures a difference in temperature between its two end points. The circuit must measure temperature where it meets the thermocouple and then add that to the thermocouple reading. Perhaps that circuit just takes a little time to stabilize?
 
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