I have a Model 133, which has selectable IEPE current limits of: 0, 4 and 10 mA. I have an application that requires a longer cable length and a higher bandwidth, which can only be met with an IEPE current level of 18 to 20 mA. Is there a modification that can be made to the Model 133 to accomplish a higher IEPE current output?
Yes, there is a very simple and easy solution to increase the output drive current. The Model 133 has BNC input connectors for ISOTRON/IEPE accelerometers. Simply attach a BNC "T" connector to channel one's IEPE input. Connect a BNC cable from another channel's IEPE input, to one side of the BNC "T" connector. Then, simply connect the IEPE accelerometer to the other BNC "T" connector.
For the model 133, the IEPE current is a common value for all 3 channels. Setting one channel to 10 mA, will set all three channels to 10 mA. To setup 20 mA of drive current, simply select any channel to 10 mA and the current will be additive for a combined current level of 20 mA, when connected as described above.
Another unique feature for this configuration is to make use of the outputs from both channels. Each channel can be setup with different gains and filtering levels for different output configurations.
See the attached photograph for this BNC "T" connection.