Updated precision bridge

An updated version of the LCR400 precision RCL bridge is now available from TTi (Thurlby Thandar Instruments). The instrument, which features a built-in 4-terminal test fixture and a full limits comparator for component sorting, now incorporates new analogue circuitry to improve the performance in terms of both accuracy and resolution.

The bridge has a basic accuracy of 0.1% for R, L and C measurements. Three measurement frequencies are available between 100 Hz and 10 kHz. The instrument is fully autoranging (with range hold) and can also automatically select the function based on the component inserted. It has dual 5-digit displays using large and bright LEDs. The second display is used for the secondary parameter of Q or D and is also used with the limits comparator for showing binning information.

It has a built-in high-quality 4-terminal test fixture that will accept most wire-ended components directly. A pair of plug-in pillar adapters enables axial components, such as bandoliered resistors, to be measured directly without bending the wires. The position of the test fixture on the instrument ensures that component bandoliers can be handled without interfering with the display or keyboard.

An external test fixture can also be used, and a capacitance null function allows up to 100 pF to be nulled out. A switchable bias voltage is provided for polarising electrolytic capacitors. The instrument incorporates a full limits comparator with binning. Up to eight pass bins can be defined along with two fail bins, and binning can be used to sort different tolerances of the same value or multiple different values. A numeric keyboard allows rapid setting up of binning values. Non-volatile memory is provided for the storage of up to nine complete instrument set-ups.

For surface-mount components, high-quality 4-terminal tweezers are available. The tweezers connect directly into the built-in test fixture of the LCR400. Four-terminal connection is made at the base of the gold-plated jaws only a few millimetres from the tip.

An RS232 interface is incorporated which allows connection to a PC and can be used to set up all measurement and sorting functions as well as store readings. PC software is supplied which allows both set-up and results logging.