-2 to -18 volts input range

[ssingh1]

Dear Friends,

We are using PCI-6221 for data acquisition which is having voltage input range of +-10 Volts.

Recently we had a requirement of connecting new type of sensors with output voltage range of -2 to -18 volts.

Is there a way to connect this input the 6221 card?

Also, Is there any other DAQ Card available for this type of input range?

Thanks

Shourya

[Buechsenschuetz]

Most A/D boards I know (not only from NI) have an input range of -10V to +10V. This is often due to input overload protection, they often use diodes to connect the input to the supply rails which usually have a voltage of -12V and +12V. Only way to connect sources with a voltage range beyond the given limits is a) to use a voltage divider, it can be composed of two resistors, the sum of the resistors should be higher than the maximum load of the source. The disadvantage is that resolution and accuracy are somewhat lower. b) you can use analog circuitry (analog adder) to add a reference voltage to the voltage of your source and thus "shift" the voltage range. 

[ssingh1]

Dear Buechsenschuetz,

Thanks for your email.

We will be considering the second option as suggested by you to reduce the voltage input range.

Shourya