Load cell+Mitsubishi FX1n(or 2n)

Hi evrebody! I got new project with Mitsubishi FX1n(but could be 2N) and load cell...now looking for anolog.to digit. converter.
Scaling range is 0-66lb +/- 0.002lb. Planning to use FX2N-4AD A/D converter which hase max.resolution of 12bits.Anlog range of
-10to10 V DC (Resol. 5v ) or -20 to 20mA. I have no experience with load cells .Could you tell me if it is right choose?

Your scaling resolution is going to cause problems. You state that the full range of the load cells needs to be 0 - 66lb, with 0.002Lb of resolution? That translates to 66lb/0.002 = 30,000 increments. 12 bits of analog resolution will only give you 2048 increments, therefore , for a 66lb load cell range, the smallest unit of measurement will be 66/2048 = 0.032 lbs of increments, more than 10 times the resolution you require.

Ian

Thank you! What is goinig to be the max. unit? And what would you advise for this scaling resolution?
Thanks again!

karlag said:

Thank you! What is goinig to be the max. unit? And what would you advise for this scaling resolution?
Thanks again!

Click to expand...

What is the application?
Is this a hopper with 3 suspended S- Beam style loadcells, or a small platform scale?

There are some basic questions that need to be answered such as:
- total live weight, the displayed weight range to be measured
- total dead weight, the weight of all pieces of equipment that are part of the scale
- type of accuracy required
- Legal for Trade application

To determine system resolution, you need to know the total capacities of all load cells, then divide the total by 4000 counts. That is a typical formula we used to use at a scale company I worked at.

Any good off the shelf load cell transmitter can give you a load cell to 4-20ma output signal, but if the scale application is wrong, it does not matter how accurate your transmitter and PLC inputs are.

Ian

This is going to be inline mixer...amount of choped rubber ,glue and water hase to be scaled(max 7lb...min 0.01lb) not in the same time,after it all mixing and scaling again(from 7lb up to 66lb) I am in the very beginig of project and do not know what kind of loadcells I need....
Thank you again.I really apprishiate!

We use serveral of the Cooper DFI Infinity Digital Force Indicators to interface our loadcells to Mits PLC's.
http://cooperinst.thomasnet.com/ite...y?&plpver=1002&origin=keyword&filter=&by=prod
We set up our parameters in the DFI and can get a High, Low, or OK discrete signal. I believe they have adapter cards if you want analog. All of our applications are just measuring force while inserting dowel pins.

Bob

You might also look at http://www.omega.com/

karlag said:

This is going to be inline mixer...amount of choped rubber ,glue and water hase to be scaled(max 7lb...min 0.01lb) not in the same time,after it all mixing and scaling again(from 7lb up to 66lb) I am in the very beginig of project and do not know what kind of loadcells I need....
Thank you again.I really apprishiate!

Click to expand...

Are the ingredients to be weighed in a holding hopper then dumped into the mixer or are to be weighed into the mixer itself ?

In order to determine what load cell type and capacities to use, first you have to determine the scale application.

From experience, to weigh micro ingredients such as your application, it is always wise to weigh up in a hopper, then dump into the mixer.

Ian

Researched a job last year and hit then 12bit problem for the PLC analogue input. I found that instead of a converter going to an analogue signal I could get one that gave out RS232/485 information, the advantage being that the converter was 24 bit. I can't find my bookmark list for the job but found this http://www.mantracourt.co.uk/products/Amplifiers_Digitisers/DSC
with a quick Google. I don't know if it would have worked because the project didn't go ahead. Also I seem to remember in discussion with various load cell supplier that the accuracy of the load cell would be an issue. Not forgetting that you then have to program to read data from the PLC comms port.

Bryan

BryanG said:

Researched a job last year and hit then 12bit problem for the PLC analogue input. I found that instead of a converter going to an analogue signal I could get one that gave out RS232/485 information, the advantage being that the converter was 24 bit. I can't find my bookmark list for the job but found this http://www.mantracourt.co.uk/products/Amplifiers_Digitisers/DSC
with a quick Google. I don't know if it would have worked because the project didn't go ahead. Also I seem to remember in discussion with various load cell supplier that the accuracy of the load cell would be an issue. Not forgetting that you then have to program to read data from the PLC comms port.

Bryan

Click to expand...

Serial Comms is always our preferred method of interfacing to weigh scales. There is no resolution lost and the problem of the weigh module display and the PLC converted weight display not matching is elimintaed.
We use Toledo Panthers with RIO on all AB applications. Only down side is the cost of each indicator and the comms module 1756-DHRIO or 1747-SN

Ian