4-20mA transducer differential circuit

4 20ma transducer

I need to display 2 pressure transducers individually and the difference between them. The transducers are 2 wire 4-20mA and the process display can handle all comon signals.
Im selecting the transducers through a rotary switch which has an OFF, PT1, PT2 and BOTH position.

Does anyone have a schematic that can produce the difference between the transducer in f.i. 4-20mA again or is something like this off the shelve available:?:

voltage to 4/20ma schematic

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converting 4-20ma signal to differential

Srammie said:

Does anyone have a schematic that can produce the difference between the transducer in f.i. 4-20mA again or is something like this off the shelve available:?:

Click to expand...

You will be converting both currents to voltages to display them (I'm assuming - with a pannel meter). Just take these 2 voltages and run them through a difference opamp circuit or instrumentation amp.

strain gauge to 4-20ma circuit

Srammie said:

I need to display 2 pressure transducers individually and the difference between them. The transducers are 2 wire 4-20mA and the process display can handle all comon signals.
Im selecting the transducers through a rotary switch which has an OFF, PT1, PT2 and BOTH position.

Does anyone have a schematic that can produce the difference between the transducer in f.i. 4-20mA again or is something like this off the shelve available:?:

Click to expand...

goto: www.analog.com you will finded 4~40mA conver ic

+atmega32 +differential adc

Better to keep an Differential Amplifier once you have converted the current to voltage.

strain gauge to 20 ma circuit

Hi,

I do not haw you planing, but if I where solve this problem, the following what I will do.

1. Get differential ADC to I2C
2. Using microprocessor, read the two channel ADC
3. To the addition in the coding
4. Display the Reading into 7-segment OR LCD, depending on the selector switch position.

BUT if you have solve this issue any other way, I will be glad to find out.

Regards
M.Pathma
www dot mypromosys dot com
MALAYSIA

4 to 20 ma schematic

HI,

U CAN CONVERT THE 4 TO 20 mA SIGNAL TO VOLTAGE BY MEANS OF VOLTAGE DIVIDER. THEN IT BECOMES VOLTAGE SIGNAL GIVE THIS SIGNAL TO ADC TO GET THE REGUIRED VOLTAGE IN SOFTWARE SIDE MAKE CALCULATION TO DISPLAY THE CURRENT .

USE 250 Ohms resistance to convert the current signal to voltage .

troubleshooting 4-20ma positioner

AD7730 is a suitable adc for your application

www.analog.com

instrumentation 4-20ma

Hi,

In a weigh scale project, I've encountered a strange problem. I've employedAD7730BNZ, ATmega32 and RS-232 serial interface to construst a logging system. In search on the net I found that somone else have had excactly my problem with AD7730 implementation. Here it is:
"I am using an AD7730BN and a strain-gauge with sensitivity 2mV/V, so the input voltage range is -0..10mV with 5V excitation. Active channel: IN1+AIN1-;

After setting up DAC and FILTER regs, applying full-scale int. calibration, the content of the gain register is insignificantly changed, but after 0-scale int. calibration, the content of the offset register is 800000 - as before calibration. After that the part is set in continuous convertion mode. After each falling edge of RDY, the data register is read, but it always is FFFFFF, independently of the input range, chop/nonchop mode or any other settings. The contents of DATA reg is FFFFFF even on the beginning - after raising edge on RESET.
Does it seem the part is demaged or is there something, that I shall take care of? I suspected that the data register was latched-up due to the power sequencing (DVDD and the system digital circuitry is powered up before AVDD), however, I used 47ohm resistors in serial with all digital inputs/outputs to avoid excessive currents. Maybe it is not enough?"
There was an suggest but unsufficint:
"AD7730 AVDD can be turned on after DVDD. In my design AVDD (5V) is turned-off in power-minimizing mode and turned-on again, when key is pressed(VDD=3.6V). All IO wires are trough 470 Ohms passed. In my oldest design no resistors are used (but AVDD is tied to DVDD=5V). In oldest design
i have one (i cannot remember what exectly) problem with ADC and decision was : DATALINEtoADC was drived to low, even
when data is readed ( trough otrher dataline). I do not why,
but in default design this code is not nessesary.
Another thing - in weighscale , which we produce, selfcalibrating of ADC is not used ( i can't remember why).
Latching (and preheating ) of chip i have see , when AGND is
not tied to DGND."

What would you suggest?Is there anybody, who would help me?

20 ma transducer schematic

Oh, so sorry for the wrong place of my question. I hope you would excuse me...!