one circuits out put voltage how to give to two seperate stages.

[joshua.svn]

Dear all,

i have a circuit ( related to temperature measurement ) whose out put is 0 to 5 v range.
can be interfaced to any micro or any display device for visual reading.
( all of little technical knowledge people can have idea about this)

I WANT THIS TO INTERFACE WITH 4 TO 20 mA AND AS WELL AS TO ONE DISPLAY DEVICE LIKE 7107 ICL.

can anybody suggest me how to design a buffer circuit with op amps without any current and voltage ( LOUDING) losses.

any suggestions ( webpages, practical schematics, formulas,tutorials) highly appreciated.

thanks and regards
joshua.

joshua.svn@gmail.com

 

[ccurtis]

Hi,

For the current loop interface, look here for a few ideas: https://www.electro-tech-online.com...a-current-loop-from-1-5v-design-ideas.131438/

 

[JimB]

Look at the attachment.

If I were doing this, I would take my 0 to 5v signal and connect it to two op amps connected as voltage followers to give isolation between circuits.

The output from one of the followers I would use to drive the 4 to 20mA converter.

The output from the other follower I would connect through a potentiometer to one of the inputs of a unity gain differential amplifier.
This potentiometer would be used to scale the voltage to give a suitable display in engineering units on the digital panel meter (ICL7107).

The other input of the diff-amp would be fed from a voltage source which is adjustable over a suitable range to give an offset to the scaled output of the diff-amp.

The scaling and offset would allow the DPM to display (say) 50.0 to 150.0 Degrees for a 0 to 5v output from the measuring device.
To do this, the output from the diff-amp would be set 500 to 1500mV for 0 to 5v input from the device.

JimB

 

[joshua.svn]

sir thanks for the idea, and it is technically true.

i have one more ??? to clarify.

could you pls tell me what is the minimum and maximum voltage we can we apply to a op amp ? ( the ic is tlo72 and supply voltages are +12 and -12) .i referred data sheet cant find?

to know for the knowledge i am asking this , shall i give 5 volts to op amp, is it right or we have to reduce voltage ang apply to op amp?

i have idea about the the gain, but how apply voltage levels like minimum and maximum voltages for op amp.


thanks and regards
joshua.

joshua.svn@gmail.com

 

[joshua.svn]

this is continuation to my ???

buffers are made by only op amps,, are there any ics which can take one input and give multi out puts

with same true copy to input to out put signal ( same frequency and magnitude )

joshua.svn@gmail.com

 

[joshua.svn]

I have one more ??? to clarify.

Could you pls tell me what is the minimum and maximum voltages we can we apply to a op amps to its inputs ?
( the ic is tlo72 and supply voltages are +12 and -12) .i referred data sheet cant find?

to know for the knowledge i am asking this , shall i give 5 volts to op amp to its input , is it right or we have to reduce voltage and apply to op amp?

i have idea about the the gain, but how apply voltage levels like minimum and maximum voltages for op amp.

this is continuation to my ???

buffers are made by only op amps,, are there any ics which can take one input and give multi out puts

with same true copy to input to out put signal ( same frequency and magnitude )


thanks and regards
joshua.

joshua.svn@gmail.com

 

[JimB]

Could you pls tell me what is the minimum and maximum voltages we can we apply to a op amps to its inputs ?
( the ic is tlo72 and supply voltages are +12 and -12) .i referred data sheet cant find?

The TL072 can take a MAXIMUM of +/-18volt supply.
It will work correctly with anything from +/- 5v to +/-15volts.

to know for the knowledge i am asking this , shall i give 5 volts to op amp to its input ,

Yes

is it right or we have to reduce voltage and apply to op amp?

The input to a TL072 must not be greater than the supply voltage, or greater than 15volts.

buffers are made by only op amps,,

Yes

are there any ics which can take one input and give multi out puts

Who knows?
Stop looking for a dedicated IC to solve every little problem.


JimB

 

[joshua.svn]

sir could you pls give me schematic, its remeved it seems.

svn.

 

[joshua.svn]

dear jimb,

could you pls give me an idea how to freeze display reading when we are using icl 7106 ic.

regars
svn.

 

[heydonms]

This isn't really my area, but I believe one solution would be to use a capacitor and buffer. The output of the circuit (or of another buffer) feeds into the cap which then feeds into the buffer. When you want to freeze it, just disconnect the cap from the circuit. The cap continues to feed the buffer which outputs to the display driver. The main downside is that the cap slows the response time, but careful selection of suitable buffer(s) and cap size should make it manageable.

A quick look at the 7106 datasheet mentions a 1pA maximum input current, so really you probably don't even need a buffer after the cap, you probably aren't going to get much higher impedance than that anyway.