# What value bias-current resistors do I use when I am making a differential connection to a data acqu

### 問題：

What value bias-current resistors do I use when I am making a differential connection to a data acqu

### 答案：

Differential inputs are more complex to use and are more expensive than single-ended inputs, but they do offer better noise immunity. The connection to a differential channel must be handled with care in order to make a proper measurement. Differential inputs generally require the addition of resistors to provide bias-current return. You can determine the value of the bias-current resistor from the value of the source resistance using the following relationships:

* When the source resistance is greater than 100 ohms: use two bias-current resistors, one connected from input high to low-level ground and the second connected from input low to low-level ground. The resistance of each of the two bias return resistors must equal 2,000 times the source resistance;

* When the source resistance is less than 100 ohms: connect the bias return resistance from input high to low-level ground. The resistance of the bias return resistor must be greater than 1,000 times the source resistance.