Marsh Bellofram BelGAS Division T2000 Explosionproof I/P & E/P Transducers - Marsh Bellofram - #1

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T2000 EXPLOSION PROOF TRANSDUCERS 29 T2000 EXPLOSION PROOF I/P & E/P TRANSDUCERS • Field-selectable inputs and direct/reverse/split ranging • Multiple input/output/mounting configurations • Precise, reliable performance under extreme conditions of temperature, vibration, orientation, supply pressure changes, supply voltage changes, RFI/EMI, humid/oilladen media, and corrosive surroundings The T2000EX is a robust electronic instrument that regulates an incoming supply pressure down to a precise output pressure which is directly proportional to an electrical control signal. The secret to the T2000EX’s precise, reliable performance under a variety of demanding environmental conditions is a patented piezo-ceramic actuator with many industry-wide firsts. APPLICATIONS The T2000EX’s precisely regulated pneumatic output can be used to operate: • Valve actuators • Chemical & Petrochemical Industries • Valve positioners • Petroleum production • Relays • Pipeline Transmission • Controllers PRINCIPLE OF OPERATION The T2000EX I/P and E/P transducers utilize closed-loop pressure feedback-control for precision pressure output and minimized effects of temperature, supply pressure changes, supply voltage changes, and mounting angle. Supply pressure is reduced by the supply valve to provide an output pressure which is internally routed to a precision temperature compensated piezoresistive pressure sensor. Supply pressure is also routed to an externally removable orifice which provides a reduced pilot pressure to a chamber containing a servo diaphragm and nozzle. Pilot pressure is controlled by modulating the gap between the face of a nozzle and an adjacent piezo-ceramic actuator, which is part of a unique patented mechanism. The piezo-ceramic actuator serves as a control link between electrical input and pressure output as follows: • The input current (I/P) or voltage (E/P) signal is conditioned to provide a normalized control signal directly proportional to the desired pressure output. • Simultaneously the output of the pressure sensor is amplified and conditioned to produce a feedback signal. • The sum of the control signal and the feedback signal produce a command signal which is delivered as a DC voltage to the piezo-ceramic actuator. • As voltage increases, the force applied by the actuator increases, so as to restrict nozzle bleed and thus increase pilot pressure. • Increased pilot pressure applied to the servo diaphragm directly causes opening of the supply valve and an increase in the output pressure until the output feedback signal and control signal combine to produce the correct command signal. FINE-TUNING YOUR APPLICATION For optimal performance in your application, the calibration of the Type 2000EX can be fine-tuned in the field. An easily-removable cover provides access to the isolated electronics. All potentiometers, connections, jumpers, and switches are clearly marked on the circuit board or on the handy chart located on the inside of the cover. The three elements of calibration (Gain, Zero, and Span) are described below. Consult the T2000EX User’s Manual for detailed calibration procedures, cautions, and instrumentation requirements. GAIN (DAMPING) ADJUSTMENT The output response of the T2000EX can be optimized for varying downstream volumes by adjusting the system gain of the control circuit. Adjust the Gain Pot counterclockwise for increased gain; clockwise for increased oscillation damping. For maximum allowable gain in your application, the pot should be turned clockwise until oscillation just disappears. ZERO & SPAN ADJUSTMENTS The T2000EX contains multi-turn Coarse-Zero, Fine-Zero, and Span adjustment potentiometers which are clockwise positive. Adjustment of either Zero Pot changes the unit’s minimum output while the Span Pot changes the maximum output. The adjustments are interactive, so it may take iterations to reach the desired calibration. WIDE RANGEABILITY The T2000EX can be field calibrated to pressure ranges other than the standard ones by combinations of recalibration, pressure range switching, and split high/low ranging. A unit should not be switched to a range outside its pressure sensor family (eg., a 0- 15 PSIG can be switched to a 3-15 PSIG, but not to 0-30 PSIG). (Caution: Do not exceed the range of the onboard pressure sensor.) For example, the easiest way to recalibrate a 0-30 PSIG unit to 3-15 PSIG would be to change the switch setting to 3-27 PSIG, then switch to split range low. FIELD-SELECTABLE FEATURES Onboard switches allow the user to easily reconfigure the T2000EX for any of several electrical inputs, direct/reverse acting, or output split-ranging high/low. Fine tuning of the unit’s calibration may be necessary after a reconfiguration. DIRECT/REVERSE ACTING Direct Acting transducers regulate to their minimum output when supplied with minimum input; maximum out with maximum in. Reverse Acting transducers regulate to their maximum output at minimum input. SPLIT RANGING–HIGH & LOW The T2000EX can be configured to regulate either half (top or bottom) of it’s normal output range, when supplied with it’s normal full-ranging electrical input. For example, a 0-10V 0-30 PSIG unit set to split range low will regulate 0-15 PSIG @ 0-10V. It will regulate 15-30 PSIG @ 0-10V if set to split range high.