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I am looking for a standalone (meaning self contained, enclosed, mountable to a wall etc) LCD display to monitor a process sensor. I would like to feed this unit a 4-20mA or 0-10VDC signal and have it display a number (4 characters max) corresponding to a scale I program.

Does anyone have a product or supplier suggestion?

I would like to purchase something off the shelf as opposed to building it, as time is a bit of an issue.

The sensor is a gas detector, which feeds into my monitoring system already. However my client wants a digital display in the area being protected. The display would read 0 to 1000 (ppm)

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closed as off topic by vicatcu, W5VO♦, zebonaut, Brian Carlton, Madmanguruman Aug 28 '12 at 17:06

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4 Answers

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What you need are these digital panel meters:

Digital Panel Meter

enter image description here

They have onboard ADC's that you can set the ADC range with resistors, and calibrate the display output with a POT usually. They are also fairly affordable and definitely simple to use.

You can usually move the decimal point with a jumper as well.

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Thats exactily what I was looking for. Found it last night, but thank you for the constructive answer. – Michael Jul 19 '12 at 17:55
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You could use a precision DAC and ADC meter from HP to display 8 digits of accuracy programmed in short order using USB or IEEE488 off the shelf.

I did this for a much larger SCADA system I designed using a 128 digit display in 1979 in an HP9825 calculator, except back then IEEE488 was called HP-IB) I used DMA access, ADC's DACs counters, MUX/DeMUX's PSU remote controls, with CRT dual-page auto alert on process control and human readable Finite State machine status and analog results refreshed every second.

What is the content of the data and how do you propose getting 8 significant figures using 4~20mA current loop?

You could have indicated if you wanted an digital interface or an analog interface.

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OP's last edit significantly changed the requirements from 8 significant digits down to 3.5. – W5VO♦ Jul 19 '12 at 1:36
8 was a typo. They happen. I indicated either 4-20mA or 0-10VDC interface. – Michael Jul 19 '12 at 17:54
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There are addressable I2C bus LCD display drivers for 4 digit control that may be cascaded.

added I2C-7SEG is designed base on SAA1064 IC.

Here is the off the shelf solution I had in mind. I2C card with LEDs in 6 colour options .. Just add plastic filter to match LED colour in a box. I2C 4-DIGIT 7-SEGMENT DISPLAY

$23 / pc.

  • 1.50 x 2.05 inches. Display brightness controllable by software.

  • Card has all address jumpers, pull-ups and 2.5V ref.

  • Flexible operating power supply voltage range of 4.5V to 15V

  • Suitable for 5.0V microcontroller

If you want an analog interface with a DAC output , use a DMM but if you have a micro and serial interface, use this.

I think for a process indicator, you need an LED display with high contrast ratio and readability from a great distance. enter image description here

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This is probably the opposite of an "off-the-shelf solution" – W5VO♦ Jul 19 '12 at 1:31
WHo knows with fuzzy requirements. – Tony Stewart Jul 19 '12 at 3:43
Dont know how the requirments were fuzzy. A stand alone LCD that can accept a 4-20mA or 0-10VDC signal and display a value. They're called panel meters. Pretty common. Indicated I would rather not have to build something from scratch. – Michael Jul 19 '12 at 17:54
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If it is a decimal number, you can interface to a large calculator keyboard and enter digits, count, decrement, increment and even scale numbers. I did this in 1976 making a small LED into a 1" x 4 digit calorie counter for an exercise machine. 3000 -0.24 = = = = = = counting down per step.

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2  
sounds fun, but not helpful – Michael Jul 18 '12 at 22:12
It was intended to be fun.. anyone who takes it serious for this Q has no sense of humour as I already entered a serious answer but your requirements changed.. oh well – Tony Stewart Jul 19 '12 at 3:24
my requirments changed because the 8 digit was a typo. – Michael Jul 19 '12 at 17:56

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