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What is the input impedance for VMIVME-3126 with -120M01 option?
The VMIVME-3126-120M01 modifies the channel inputs using a resistive voltage divider with a ratio of 0.2 which gives the required +/-50V range. This divider is implemented with 10Mohms in series with the channel Hi input followed by 2.49M ohms to the channel Low input. These resistors are +/-1% tolerance. Assuming there are no connections to the channel RTD pins, the nominal input impedance should be 12.49M ohms +/-1%. The input channels are buffered using an AD706A op amp configured as a voltage follower. This part has a max input bias current of 150pA, therefore input circuit loading should not be significant.