GPM Gauge problem

Hi all, I am in need of some help with making logic to run a GPM gauge.
I am using Siemens Step 7 ver 5.4, a 315-2 DP PLC, a Red Lion CUB5R000 Digital read out gauge, and a Hoffer Flow Meter conected to their CAT2 Pulse input module that converts to a 4-20mA output. (the hoffer flow meter sends a pulse each time a fin passes a pick up head - I believe there are 6 fins on the wheel - There are X amount of pulses in one gallon of fluid flow) The read out gauge is mounted in a remote box and the signal is by way of Profibus to a ET200M IM153-1 Profibus interface.

How do I go about making the logic to convert the 4-20mA signal into a output for the gauge to read?

thank you

I had to read your post a few times to get a grasp of your actual problem.

What I interpret is: You have an analog signal and want to convert this into an integer to display on a digital gauge. Correct?

If that is the case, then you need to calculate the relationship between the analog output and the actual flow. This information should be available in your documentation of the meter and analog converter.

Once you know that a given value (which will be converted into an integer form by the analog card) you can do a simple math equation to get your true value.

You would then pass this value into the tag that will eventually be passed to the read-out.

I am guessing that this isn't the final answer you need but it should get use started in the right direction.

Your system reads as:

Flow pulses -> 4-20ma -> plc -> output pulses -> cub

why not feed the flow pulses direct to the cub ?

L D[AR2 said:

Your system reads as:

Flow pulses -> 4-20ma -> plc -> output pulses -> cub

why not feed the flow pulses direct to the cub ?

Click to expand...

L D[AR2,P#0.0] it is connected at a remote location and the communication is profibus, the pulse rate would be faster then the PLC could handle. The Cub5 uses a pulse signal to count.

So the plc must convert 0-10 gallons/hour to 0-10Hz for example.

This is the information off the data sheet.
F (max) = 506.1 Hz @ 130 GPM
Analog span 4 to 20 mA
K-Factor of metering system: 233.580 Pulses per Gallon

Am I missing something - why doesn't the plc output an analogue voltage to drive a voltmeter scaled to display gallons/min ?

i.e. Why are you using a counter display ?

The gauge is used to measure fluid flow at any given time, and needs to hold the count once the flow stops. It is also able to have the count zeroed out.

Replace the CUB5 with something that takes a 4-20mA input, or per L D[AR2,P#0.0] said, connect the flowmeter to CUB5 directly.

I still can't understand your description of the connection. List your connection one by one. From what you said, I gathered that you have the following..

A. Flowmeter (Pulse OUT)
B. PLC CAT2 (Pulse IN)(Profibus ??)
C. Profibus (IN and OUT)
D. Redlion CUB5 readout (Pulse IN)

beyond that, I don't understand what you are trying to do and WHY.

Oh, ok. I posted the above while you were posting.

Why not get a small panelview to your PLC? Have the PLC do the count and HMI for the display and reset function.

I have a Hoffer flow meter that sends 233.580 pulses/gal to a exchange device that changes the pulses to a 4-20 mA output signal, I am using a Siemens 315-2DP PLC and communicating via Profibus to a remote panel using a Redlion CUB5R000 counter/rate indicator.

There are CUB5s that accept analog, thermocouples, pulses, etc. The family has really expanded this past year.

But, you have a pulse input CUB5, so I imagine that you're connecting the pulse signal directly to the CUB, or at least paralleling the signal to it?

If so, the scaling is...

Rate DSP of 100 (desired reading)
Rate INP of 389.3 (hz)

It's a ratio you're establishing, so any two values with the same ratio would work.

At 100 GPM, the CUB5 would "see" 23,358 pulses per minute based on the information you gave on the sensor. However, the INP value must be in Hz, so divide by 60, and you have 389.3. Make sense?

However, the more I read your original post, the more I think you're converting the signal prior to the CUB5. If that is the case, what signal do you want/how do you want to provide an input to the CUB? Are you asking how to create a scaled pulse train from an output on the PLC, such that you can pass the data to the CUB that you have?

Jesse

normally we use a signal splitter to divide the pulse current from the flow meter to the gauges and enter the pulse rate for the readout calculations, however, for this application the flow meter pulses are being converted into a 4-20 mA signal and are inputted into a Siemens analog input card. a remote is being used that communicates via profibus and has a Siemens IM153-1 profibus interface module. the signal needs to be scaled for the Redlion CUB5R000 counting gauge that is being used in the remote. since the gauge counts by a pulse rate, i need to have the 4-20 mA inputted current converted into a pulse output rate to be sent via profibus to the remote which has the counting gauge.

Hope that helps explain the situation better.

So is there a digital output module on the Siemens IM153-1? Is that what will be connected to the CUB5?

yes