设置
快速交货
免运费
国际贸易术语
支付类型
市场产品
If the components in front of the instrumentation amplifier are set up in such a way that they create voltage dividers, it can easily ruin the common mode rejection (CMR) of the In Amp. As a general rule, resistive dividers should not be used for attenuation before the instrumentation amplifier. Any resistors connected in series with the inputs should be several orders of magnitude smaller than any resistors connected from the inputs to ground. Even in this case, as much care as possible should be taken to match negative and positive input paths. If attenuation of the input voltage is needed there are three options. First, run the instrumentation amplifier on large enough supplies to handle the input voltage. Then attenuate after the instrumentation amplifier. This method has the advantage of preserving the instrumentation amplifier’s high input impedance, so that the sensor’s source resistance can be ignored. Secondly, do the attenuation before the In Amp using an expensive matched resistor network. By buying a precisely matched networked the attenuation at the negative input can be matched to the positive input so there is little degradation in CMRR. The last option is to use a difference amplifier such as the AD8276, AD628, or AD629. Unlike instrumentation amplifiers, difference amplifiers can measure beyond the rail.
