The I400 four-channel electrometer combines sensitive current measurement with the ability to bias the signal measuring circuit up to 400 V relative to ground. This makes it suitable for reading out miniature ionization chambers. These chambers typically provide the signal on an electrode which must be a few hundred volts relative to ground to bias the chamber. This feature requires the use of triaxial signal connections to eliminate unwanted leakage currents in cables and connectors. Up to now the I400 has been supplied with 3-lug triaxial bayonet connectors. Customers may now request the widely-used TRT threaded triaxial connector. This allows direct connection of a wide range of proven dosimetry chambers.