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Flowmeter with two 4-20mA outputs to a PC

Flowmeter with two 4-20mA outputs to a PC

Flowmeter with two 4-20mA outputs to a PC

Please let me start by saying I am not an electrical engineer, I am a software developer. I have a current project where I need to connect a Flowmeter which has two 4-20mA outputs into a management system (A specialized PC). I need to be able to differentiate between the two inputs.

The PC has only a single RS232 or an Ethernet port.

I will attach the specification of the Flowmeter to this posting.

I have tried searching the Internet for 4-20mA convertors and have found quite a few, but I feel out of my depth in determining which is the best way to go.

Any help would be greatly appreciated.



RE: Flowmeter with two 4-20mA outputs to a PC

A couple of options come to mind, but you must really determine your data response requirements to move forward.  The conversion of analog signals to a digital number has the inherent penalty of time delay and resolution.  More timely / more accurate measurements and conversions cost more in money & implementation time.

you could find a PC plug in card that accepts analog input and with proper configuration will accept 4-20mA.  Search keywords would be "digital to analog converter", "DAC", "data acquisition", and similar.  Omega Engineering www.omega.com pops into my mind as a typical source for this stuff, but certainly there are many more sources.  Typically those devices give you access to data registers across the data bus, so your PC program can read data directly from a memory location.

another method I've used that is workable, usually cheap, and very flexible is to use a cheapo PLC (like AutomationDirect or equivalent) with a suitable analog input card.  It's amazing what is out there on the market.  Once you read / convert the analog signal, then you can send it out to whatever device via whatever media like Ethernet, serial, DeviceNet, or many other industrial network protocols.  But then you must worry about the processing time lag.  If your needs are superfast, then this is probably not the correct path.

Blue Technik LLC
Virtuoso Robotics Engineering

RE: Flowmeter with two 4-20mA outputs to a PC

my approach would be to search for an embedded controller with onboard AD converter. There are many. You will also find many that have multichannel inputs with RS232 output assembled on mini boards.

The question you'll need to resolve is do you isolate the input from source. Again there are many offerings.

You will simply drive your 4-20ma over a resistor and do a voltage conversion. Your controller will need to know if it waits for a conversion/comm command, or continuosly converts/comms.

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