How to measure 12V input frequency signal on AI pins of USB-6009

[qasimp]

Ma

ximum voltage that can be connected to analog

inputs is from -20 V to 20 V (card specifications

Ma

ximum voltage that can be connected to analog

inputs is from -20 V to 20 V (card specifications

Ma

ximum voltage that can be connected to analog

inputs is from -20 V to 20 V (card specifications

Maximum signal that can be measure in 6009 AI Analog Input pins is -10 V to 10 V as per spec. I want to measure a 12V freq signal 0.1Hz to 2000Hz with 50% DC. Do I have to scale it down to 5V or can directly connect to 6009 AI pins. If need to scale down what are my options. My signal is pulled up to 3.3K+100Ohm resistance.

Waiting for quick response.

[Henrik_Volkers]

Using a voltage divider is the standard solution.... 

Look at the spec how the input schematic of a 6009 looks like. If I remember rigth, a simple 100k Resistor in series with your signal should do the job. (IIRR the input impedance is in the 100k range, so together with an 100k resitor at the input you get about half the voltage). Improvements can be made if you match the input capacity too ( likewise the 10x scope probes) ....

[SnowMule]

Voltage divider, then multiply it back in software after you read that voltage.  Pretty typical measurement technique till you get to really high voltages, then you get to play with HV differential probes.

Also, if you're developing a battery system that uses that battery to power it, dividing that voltage and reading it on the A/D then multiplying it in firmware is about the only way to measure the battery's voltage.