load sensors

[hifimike]

Does anyone know the best and cheapest load sensors on the market. also whats the best/cheapest one to use with these load sensors. If possible I would like to get away from using an amplifier for the inputs. Does any plc have a mv analog input

 

[Lancie1]

hifimike,

I have heard "load" used to refer to ampere current load on various devices, weight load on load cells, heating or cooling load on HVAC system, even lighting load on a circuit breaker panel. Which one is it that you are needing to measure?

No not every PLC has a MV input built-in. For most of them you will need to buy the proper Input Module to allow for a milivolt input, but there are a few that have 1 or two milivolt inputs built into the unit.

If you are measuring current load in Amperes, then you can use an external current transducer to convert Amperes to a miliampere (mA) signal. If you are measuring temperature, then you need a thermocouple input module that allows milivolt input signal levels.

If I only knew what type of load sensors you are talking about, I or someone else, might could reccommend a brand.

 

[Eric Nelson]

You'll also have to decide between 'best' and 'cheapest'. You can't have both!... :nodi:

beerchug

-Eric

 

[hesham]

I think he means Load cells

hifimike
I think there are a lot of anerican suppliers for loadcells i know from them Ricelake with a good price.From the PLC point of view you don't need a module with mv input the type of signal is not the main issue in this case.you should look after the resolution of the A/D converter for this module as well as the sampling time because whighing systems need fast processors with the low sampling rate and a high resolition A/D.
I know that Schneider & Siemens have a wheighing modules in which you can connect the load cell directly to it.schneider wheighing module have 20 Bit resolution i don't know what is the resolution for the Swarex(By Siemens)
Any How it's not Cheap at all.

 

[Thomas Sullens]

hifimike
Mike are you wanting to weigh something or monitor current?

 

[Tom Jenkins]

Based on your "mV" question, I'm going to assume you mean strain guage type load cells for weighing applications.

I've had good luck with Sensotec over the years, and I know Omega Engineering has them, but they of course are usually higher priced for a small volume user. Have you searched the Thomas Register site?

Quite a few PLCs haveI/O cards that can take the mV signal directly, and in many cases thermocouple (T/C) cards can be configured to take a linear mV signal. The AutomationDirect.com PLCs, for ecample, have this kind of module in a number of models.

Are you sure you want to do this, though? mV signals are incredibly susceptible to noise, and unless the PLC is in very close proximity to the load cell, or you are in an incredibly benign environment, you will not get a clean signal and will be fighting inncaccuracies for the rest of the machine's life. It can quite often be very, very expensive to save money with cheap components.

 

[gbradley]

We use Toledo Transducers
Toledo

I highly recommend their products. Very Robust in a tough environment.
But then again, that's all I am familiar with. There may be something better out there?