Dual Channel Differential Electrometer AMPLIFIERS, ELECTROMETERS l High input impedance (10 15 Ω) l Differential (A-B) output l Low noise and wide bandwidth l Electrode resistance test circuitry l Probe test circuitry l Driven guard shield the probe input maintains the specified high resistance and reduces the stray capacitance of the probes. Careful design, coupled with quality component selection, particularly in the headstage, results in an excellent amplifier with low noise and wide bandwidth. The FD223a will faithfully reproduce the measured signal. To reduce the noise and stray capacity even farther the probe housing includes a signal driven guard. A portion of this inner driven shell is exposed at the probe tip allowing a spring shield to be extended over the electrode holder and microelectrode. The amplifier features a probe test port that permits testing of the electrode test feature and setting of the probe leakage current, (IG). A standby mode is included and should be used when attaching glass microelectrodes or electrode holders to the probe input. While in the standby mode the voltage at the probe input is clamped near zero volts thus protecting the input. The FD223a is a dual differential, high impedance amplifier/electrometer designed specifically for electrochemical measurements using ion specific (K+, Na+, C1-, etc.) or pH glass microelectrodes. The instrument is very stable, drift free, and features a built in provision for measuring and adjusting input leakage current. DC levels may be independently adjusted for each probe channel. The ability to locate the sensing probes directly at the measurement site overcomes the noise introduced by the long cables usually needed to bring the measured potential to the instrument. Signal-driven guards at FD223a SpECiFiCationS INpuT ImpeDANCe INpuT CApACITANCe LeAKAGe CurreNT GAIN OuTpuT reSISTANCe INpuT SWING VOLTAGe rISe TIme (10 TO 90%) BASeLINe STABILITy pHySICAL DImeNSIONS pOWer prOBe HANDLe SHIppING WeIGHT > 1015 Ω, shunted by 0.5 pF 1 pF, nominal 75 fA max 1.000 ± 0.1% 50 Ω ±10 V 5 µs, small signal ±0.1 mV/day Case: 8.8 x 21.0 x 17.5 cm (H x W x D) probe: 12.7 x 65 mm (D x L), 1.8 m cable 90-265 VAC, 50/60 Hz, 10 VA 6.5 x 65 mm (D x L) 2.5 kg #2547 Driven Guard Shield FD223a FD223a Dual Channel Differential electrometer 2 probes, driven guard shields and micropipette holder MEH1SF included for all glass microelectrodes O.D. 1.0 mm, 1.2 mm, 1.5 mm, or 2.0 mm. optional M3301l M-3 rC1t 2547 MEH1SF FD223ap aCCESSoriES micromanipulator (specify left- or right-handed) 80° Tilting base reference cell (Ag/AgCl) Driven guard shield for FD223Ap probe microelectrode holder replacement probe (includes calibration) See cables and connectors, page 108 See microelectrode holders, page 120 See capillary glass, page 114 NOISe (0.1 Hz TO 10 KHz) <100 µV p-p, input shorted pOSITION CONTrOLS rANGe ±600 mV OperATING CONDITIONS equipment is intended to be operated in a controlled laboratory environment. Temperature: 0-40 °C; altitude: sea level to 2000 m; relative humidity: 0-95%. 72 World Precision Instruments UK: Tel: +44 (0)1462 424700 • wpiuk@wpi-europe.com www.wpiinc.com Germany: Tel: +49 (0)30-6188845 • wpide@wpi-europe.com US: Tel: 941-371-1003 • sales@wpiinc.com