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 Post subject: LM34DZ - Usable with an Analog Panel Meter?
PostPosted: Aug Wed 28, 2019 7:43 am 
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Greetings
I have several LM34 DZ Fahrenheit temperature sensors. This device outputs an analog voltage which is 10 mV DC per degree F.
I have used them with DMMs and DC digital panel voltmeters. They are a very good way to measure temperature.
Out of curiosity, the idea of connecting the output to an analog DC volt panel meter came to mind.
Using a series resistor or potentiometer and a panel meter with, for example, more sensitivity than 120 mV FS, might work.
But I don't what the output current capability of the LM34 DZ is.
Thanks for your thoughts on this, C-N-E

LM34DZ datasheet: https://www.allelectronics.com/mas_asse ... LM34DZ.pdf

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 Post subject: Re: LM34DZ - Usable with an Analog Panel Meter?
PostPosted: Aug Wed 28, 2019 11:45 am 
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Data sheet lists 10 ma as absolute maximum output current.

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 Post subject: Re: LM34DZ - Usable with an Analog Panel Meter?
PostPosted: Aug Wed 28, 2019 1:02 pm 
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I used one many years ago to drive an op amp which, in turn, drove a meter. I never tried to drive a meter directly.

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 Post subject: Re: LM34DZ - Usable with an Analog Panel Meter?
PostPosted: Aug Wed 28, 2019 7:33 pm 
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A better data sheet here: http://www.ti.com/lit/ds/symlink/lm34.pdf
On page 14 you'll find this:
Attachment:
LM34 Analog Temp App.jpg
LM34 Analog Temp App.jpg [ 29.34 KiB | Viewed 922 times ]

No indication (no pun intended) of the meter characteristics, but a microammeter, not a voltmeter is indicated by the use of a series resistor. A 100uA meter would not overtax the device spec as it's 100th of the absolute maximum output current.
John

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 Post subject: Re: LM34DZ - Usable with an Analog Panel Meter?
PostPosted: Aug Wed 28, 2019 10:25 pm 
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LM34-LM35 App note from National Semi:

Attachment:
LM34-LM35 temp.pdf [190.99 KiB]
Downloaded 104 times

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 Post subject: Re: LM34DZ - Usable with an Analog Panel Meter?
PostPosted: Aug Wed 28, 2019 11:23 pm 
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OldWireBender wrote:
A better data sheet here: http://www.ti.com/lit/ds/symlink/lm34.pdf
On page 14 you'll find this:
Attachment:
LM34 Analog Temp App.jpg

No indication (no pun intended) of the meter characteristics, but a microammeter, not a voltmeter is indicated by the use of a series resistor. A 100uA meter would not overtax the device spec as it's 100th of the absolute maximum output current.
John

Thanks! Now that's what I call a DATASHEET
Exactly what I was looking for.

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 Post subject: Re: LM34DZ - Usable with an Analog Panel Meter?
PostPosted: Aug Wed 28, 2019 11:30 pm 
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Findm-Keepm wrote:
LM34-LM35 App note from National Semi:

Attachment:
LM34-LM35 temp.pdf

Thanks, Findem K.
I have a few 0-100uA FS panel meters. Time to gin one up with the LM34.
One could probably drive quite a few of them in parallel to be viewed in multiple locations...

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 Post subject: Re: LM34DZ - Usable with an Analog Panel Meter?
PostPosted: Aug Fri 30, 2019 11:36 am 
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OK, I dug up from the panel meter tub a Simpson 3 1/2" Century Series 0-100 uA model. I guessed at a value of 10 Kohms for a potentiometer for the current limiting resistance, The actual resistance needed was 8.45 K.
With the LM34 output connected to my Fluke DMM, bridging the Panel Meter and its series resistor in parallel with the DMM did not reduce the output voltage by even one millivolt.
I would call this little project "another random success", and I thank all who responded for their assistance.

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