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PLC Pie Guy
April 8th, 2015, 05:21 AM
Good morning all.
I am looking to purchase a loop calibrator.
I am looking at a particular model with different options but I have one question.
What is the difference between simulating and generating when referring to Ma and 0 - 24 VDC?

Thanks

geniusintraining
April 8th, 2015, 05:32 AM
We sell this one and for the price its a great deal, we have sold a lot and have had very good feedback from them

http://www.plccable.com/milliamp-current-volt-generator-4-20-ma-0-10-vdc-epro-with-case-leads/

If you are just looking to read we have a Fluke 771 and 772 if your going to generate the signal then the 707 is a good model but I am out

Not sure if they go to 24vdc, when I needed to go to 24 I used a variable transformer

To me simulating and generating are the same

DwSoFt
April 8th, 2015, 07:03 AM
I love my fluke 772. pricey but worth it. The clamp is nice for troubleshooting without breaking the loop

diat150
April 8th, 2015, 07:39 AM
I like the fluke 725. its expensive but it can do everything.

DwSoFt
April 8th, 2015, 07:42 AM
The 725 is awesome but it doesn't have a milliamp clamp meter. .. Also I prefer the seperate ones for temperature and milliamps because A. If 1 fails or needs sent in for calibration I still have the other meters. B. simpler menus

osmanmom
April 8th, 2015, 08:05 AM
i use fluke 789

Tom Jenkins
April 8th, 2015, 08:15 AM
A little speculative here, but I think the manufacturer is using simulate for a two-wire device where the 4-20 mA signal is loop powered external to the calibrator. Generate would be using the calibrator's own power to source the 4-20 mA signal the way a four wire device does.

boneless
April 8th, 2015, 08:47 AM
I think Tom is right, many calibrators have different modes:

Read 4..20 mA - ext 24 VDC
Read 4..20 mA - while supplying 24 VDC
Simulate 4..20 mA - ext 24 VDC
Simulate 4..20 mA - while supplying 24 VDC

4..20 mA often is 0..22 mA

shooter
April 8th, 2015, 01:40 PM
search this forum for loop calibrator or LM317 (the IC used in it.

rdrast
April 8th, 2015, 01:54 PM
If you need an actual calibrator, and not just a test device, you will have to spend the money to get something traceable and calibratable.

If you just need a test device that is generally accurate, almost any meter that has the functionality you want will do.

dogleg43
April 8th, 2015, 02:49 PM
This Altek model is very simple to use and rugged.
Will work like Tom said in his post.

I'm not sure how cost competitive it is but it is very handy and portable.

https://www.google.com/#q=altek+loop+calibrator+model+334

NetNathan
April 8th, 2015, 04:03 PM
^2nd Altek.
They make some nice compact calibrators.
Process Loop Calibrator (334A) that it is very accurate. Accuracy (0.03%, Within 0.02 mA from 4-20mA).
http://www.testequipmentdepot.com/altek/pdf/334a.pdf

They make a sweet 14-type Universal Temperature Calibrator (442) also. Accuracy (0.008% of reading + 0.006 mV).
http://www.testequipmentdepot.com/altek/pdf/422.pdf

Of course Fluke is supreme...but costly.

JRW
April 8th, 2015, 04:31 PM
Transmation
The best you can buy

Bering C Sparky
April 8th, 2015, 11:53 PM
+1 for the Fluke 789, can read Ma without breaking the loop.
read, simulate, source, step, + volt ac/dc, ohms, its got it all in one package.
Cost some $$$ but well worth it.

shooter
April 9th, 2015, 01:22 AM
a simulator only has a control in it, thus works without battery.
in a generator a battery is added to the loop, So you wont need the power supply, and can control a sensor without any connection.

geniusintraining
April 9th, 2015, 06:28 AM
+1 for the Fluke 789, can read Ma without breaking the loop.
read, simulate, source, step, + volt ac/dc, ohms, its got it all in one package.
Cost some $$$ but well worth it.

Hey BC, the 789 still needs to break the circuit (loop) but the 77x is the clamp model that you do not have to break the circuit, I can save you some money if you are looking for either one we have them both

For a low price 4-20 simulator THIS ONE (http://www.plccable.com/single-channel-4-to-20-ma-current-loop-simulator-troubleshooting-tool/) is very good, and they are made by a PLCTalk.net member and my other ones (other then the Flukes) are also made by him, these are great quality and for the price can't be beat, when we first started I was just looking for a simple device to test some pneumatic valves that were on the 8th floor and the controllers were on the 1st floor... it took two people to setup and calibrate a valve or I had to walk down and back up, but after he made the first model we were able to do it with one person and not have to have a 1,000 dollar meter, I sell a lot of the Flukes but most people dont want toss them into their tool bag, its easier to put in a 50.00 dollar model in with the hammer, I have been very impressed with what he has done with his business and the products that he has been able to create

This is a link to some of his products http://www.plccable.com/brands/Troubleshooter.html

Bering C Sparky
April 9th, 2015, 09:34 AM
Hey Mark,
You know a couple of years ago I said the same thing to an old integrator who was on one of our vessels, and he proved me wrong also.

I would not believe it had I not seen it with my own eyes, try it out if you have a 789 laying around.

geniusintraining
April 9th, 2015, 10:14 AM
I have about 20 in stock... how are you going to hook up without breaking the circuit ? the 77x has a small clamp that will clamp the wire and read the MA signal

Look at the picture of this 771 http://www.plccable.com/fluke-771-milliamp-process-clamp-meter-4-20ma/

The only way I have connected the 789 is in series and I had to break the line to make the connection

mbartoli
April 9th, 2015, 10:45 AM
We have the Fluke 773 and find it wonderful. Can be used in series in the loop or as a clamp-on without breaking the connection.

As others have stated; the most versatile devices can measure or simulate on an externally powered loop, or read/measure or source/generate by providing the loop power. Sourcing or simulating must be done with the meter in the series circuit, not using the clamp.

Bering C Sparky
April 9th, 2015, 10:56 AM
I know what you are saying, but where you can get to the terminals as test points, try to test ma using the 789 by just touching the terminals, dont break the loop.

I did not believe it either, but seeing is believing.

shooter
April 9th, 2015, 03:58 PM
when using knife connectors it is possible to check the current, by putting the leads ate one connector and open the knife.

jtashaffer
April 9th, 2015, 06:43 PM
Try Durck millamp meter.

ethanfloweigh
April 9th, 2015, 09:40 PM
I've never understood the purpose of using expensive 4-20mA calibrators on PLC's or other kinds of remote readouts because they don't reflect a true measurement value in most cases.

In order for your reading to be accurate, you have to run tests on whatever device is supplying the current anyway to know what their true current output is, and then you have to simulate that current into the PLC with your simulator/generator.

I don't know what you're trying to accomplish, but calibrating whatever target device you're using on site while leaving it tied into the PLC and scaling the signal to match is the most accurate way of doing it.

ethanfloweigh
April 9th, 2015, 09:45 PM
^ All that being said, I have seen a handheld Fluke in the field that read current accurately just by touching the leads to the terminals.

I believe this has something to do with a resistor and a high frequency signal being passed through, because I believe many HART interfaces have this feature as well.

Tom Jenkins
April 10th, 2015, 08:32 AM
... I don't know what you're trying to accomplish, but calibrating whatever target device you're using on site while leaving it tied into the PLC and scaling the signal to match is the most accurate way of doing it.

I have rarely used a calibrator to "calibrate" anything. Most often when I did I was scaling meters, digital displays or signal conditioners. However, a calibrator is an enormously useful trouble shooting tool for field service and panel building.

osmanmom
April 10th, 2015, 08:55 AM
the expensive tool means to give the best/high quality result to customer

and

the cheap tool means to give our best that we can afford to customer.

osmanmom
April 10th, 2015, 08:58 AM
how to choose the tool depend where we work

osmanmom
April 10th, 2015, 09:04 AM
during commissioning on instrument equipment what suitable tools to be when power not

available and offline

diat150
April 10th, 2015, 10:11 AM
The 725 is awesome but it doesn't have a milliamp clamp meter. .. Also I prefer the seperate ones for temperature and milliamps because A. If 1 fails or needs sent in for calibration I still have the other meters. B. simpler menus

point taken, but it could easily be said that you now have to keep track of calibrations of 3 different pieces of equipment and the fact that you are more likely to have have 1 of 3 pieces of equipment to have a failure than just 1 single.

I also dont get the argument for simpler menus. the 725 is very simple, and very powerful.

If you absolutely need a clamp meter you can purchase one.