# Need 0-5 ma to 0-20 ma converter

J

#### Jim

Could anyone help me with this (probably) incredibly simple electrical problem?
I need to up-scale a signal from a A/D board from 0-5 ma to (0) 4- 20 ma to
drive an FMC vibratory feeder controller. FMC gave me a schematic for using
the alternative 0-10 volt input, but my technican can't figure it out. I've
been in India for three weeks, and should get your repplay about when I get
back to the states to try to tackle this.

(If this sounds stupid, it's because I'm a Chem E, not a elctrical
technician... )

=>Jim<= Now in Amsterdam for a few
days....

B

#### Bob Hogg

Hi- Enjoying the Country.

1 to 10 is resistive and works just like a 3 wire rheostat. +, - and signal. If you put 10 VDC in the device and 5 comes out, then the action is in the middle.

Once you have this you can use our 4-20 converter. All it needs is an input and a power supply and you have 2 wires, 4 – 20 out.

Cut and paste http://www.almegcontrols.com/
and go to products, controls, 4-20

Usually have them ready to go.

Thanks Bob Hogg

K

#### Ken Irving

Most (probably) devices accepting a current signal input run
that current through a resistor, and actually sense the resulting
voltage drop across the resistor. You can use Ohm's Law (V=IR)
to relate current, voltage, and resistance. If the controller
can accept a 0-10 volt signal, and you have 0-5 mA available,
then you want R=V/I, R=10/0.005=2000 ohms, as the load resistance
connected between the controller's voltage input terminal and its
signal ground. You'll have to check to see that the 0-5 mA current
source is capable of driving that current through 2K ohms load.

If you want/need to convert 0-5 mA to 4-20 mA you'll need to use
a convertor or retransmitter device designed for the purpose.

In all cases, it is important that the signal grounds or commons are
compatible between the signal source and controller, and any devices
power supplies and cannot be wired together, common-to-common,
then some means of isolation will be required.

--
Ken Irving <[email protected]>

C

#### Chris Shea

Jim:

Moore Industries makes a converter for any span of 1mA or more between -2.5mA and 55 mA with a 4-20mA output. They are the SIY or SDY (with local display) models. Check out www.miinet.com.
Good Luck

Chris Shea

J

#### Jim

I wasn't very clear about the sink capability of the A/D card. It can only
drive 0.005 amp, so it cannot easily drive a resistor to make )-10 volts. Put
another way, if the designer expected 4 - 20 ma, he/she seems to expect more
than 5 ma source capability at the 0-10 volt input.

I'll keep watching.

=>Jim<=

X

#### Xueqing Liu

Jim:

Phoenix Contact has what you need, at least two of their products meet your
requirement: MCR-c-ui-ui and mcr-clp. Web page: www.phoenixcontact.com and phone
number in US: 717-944-1300.

Claire Liu

K

#### Ken Irving

I'm not sure how you conclude that the 0-5 mA driver cannot drive a 2000 ohm load (to yield 0-10 V), but apparently you have other information that clarifies that.

I copied your subject into a google.com search and found a number of hits, e.g., ADTECH ISOLATORS at

There are lots of options out there.

Ken

I

#### ianingram

Red Lion Controls make a 'universal' signal conditioner that can be programmed via DIP switches which should suit your needs.

Please email me if you require further info;
[email protected]

B

#### Barrington

> Could anyone help me with this (probably) incredibly simple electrical problem?
> I need to up-scale a signal from a A/D board from 0-5 ma to (0) 4- 20 ma to

Are you sure you don't have a 0-5V signal from your board?

B

#### Barrington

> I wasn't very clear about the sink capability of the A/D card. It can only drive 0.005 amp, so it cannot easily drive a resistor to make )-10 volts. <

Just picked up this message. Jim, it appears you have a VOLTAGE O/P from your A/D card which is capable of driving 5mA max. The Input module you are connecting to (0-10V) will have a very high impedance so the current will be minimal.

What is the O/P range of your A/D card? If it's already 0-10V you're laughing, if it's 0-5V then you need scaling.