# LM3916 24V measurement

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#### oriol

##### New Member
Hi everyone, I bought an LM3916 device to measure a 24V battery level, but there are only example circuits for 1.2-12V signal source, so I don't know if it's posible to design a circuit to measure those 24V. could it be posible?
Thank you

#### 3v0

##### Coop Build Coordinator
Forum Supporter
What you need is a voltage divider.

It is an easy concept to understand. Because each of R1 and R2 are identical. They each must drop 1/2 Vin.

Make R1 and R2 10K. Connect the voltage you need to measure to Vin. Connect Vout to the LM3916. When Vin is 24V Vout will be 12V.

3v0

#### oriol

##### New Member
yes, that's what I thought but, does it really work? I mean, does the LM3916 measure correctly the batteries state with a voltage divisor?

##### Banned
Why wouldn't it? It's a 12V lead acid vs a 24V lead acid, scaled down they have the same curves.

#### crutschow

##### Well-Known Member
yes, that's what I thought but, does it really work? I mean, does the LM3916 measure correctly the batteries state with a voltage divisor?
As Sceadwian stated, it will. A resistor divider is perfectly linear. Thus the LM3916 output will be a proper representation of the 24V battery voltage.

The LM3916 is designed for an audio VU meter, which has a non-linear output. If you wanted a linear representation of the voltage, you would use the LM3914.

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#### oriol

##### New Member
oops, yes, I thought 3916 was the linear one.... it's a logaritmic one then isn't it? I'd better use the LM3914.

Thanks

#### oriol

##### New Member
Is there another way to do a batteries measurement with some simple chips like LM3914? I say that because the LM3914 only goes to 5V..... and I need to measure 24V. The LM3916 goes to 12V but it's not linear

#### crutschow

##### Well-Known Member
You just use a voltage divider as previously described to drop the 24V to 5V.

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