I will measure resistance in the rang von mOhm and I want to use the Agilent 34970A, but the measurment rang is only 100 Ohm! I have also the 34901A avaiable! Is there any possibility to do this defiance the high measurment rang? For Example gives any measuring board for the 34970A to do this??
Using the 34970A 100 Ohm full scale range at the NPLC 10 (6 ½ digits resolution) gives a resolution of 0.1 mOhm. However, the 1 year accuracy for a 1 mOhm measurement is +/- 0.004% of the range or +/- 400 mOhm, so the 34970A is not a good instrument for this measurement. The proper instrument for this measurement is the 34420A nanovolt/uOhm meter.
Performance verification to within the accuracy specifications is done at 0 ohms and full scale. The 0 ohm, 1 year accuracy is +/- 4 milliohms. The 34970A can read 0.000 mohms, but this is only accurate to +/- 4 mohms. This is a 4-wire resistance measurement. 2-wire resistance is not calibrated separately. The typical closed channel 2 wire resistance reading for a new 34901A channel is < 1 ohm. See also note 6 in the 34970A Data Sheet Accuracy specifications:  Specifi cations are for 4- wire ohms function or 2-wire ohms using scaling to remove the offset. Without scaling, add 4 Ω additional error in 2-wire Ohms function. If more than 4 ohms is measured, the 34901A is worn out and should be replaced. Hi accuracy, low resistance measurements should always be done using the 4-wire resistance measurement function.