500 Series Isolated 4-20 mA Transmitters

ISOLATED 4-20 mA TRANSMITTERS

500 SERIES FOR DEMANDING APPLICATIONS
Isolated to 1500 V rms
Two-Wire 4-20 mA Operation
9-50 V Compliance
Turndown Ratio to 10:1
NMV Protection to 120 Vac
-40 to +85░C (-40 to 185░F) Operation
Shock Resistance to 55 g
NEMA-4X Metal Case
Field-Scalable

UNMATCHED ELECTRICAL PERFORMANCE
Two-wire Operation
Power is obtained directly from the 4-20 mA loop, with no need for separate power input. This simplifies field wiring and eliminates the possibility of noise pickup from power lines.

Isolation to 1500 V rms (2100 Vp)
This exceptionally high CMV rating from the input to the case or output eliminates the possibility of electrical ground loops between the signal source and the receiver. It also provides a high degree of protection for the receiver against electrical hazards, such as accidental contact between the signal source and an AC power line.

9-50 V Compliance
The loop voltage driving the transmitters can be from 9 to 50 V without loss of accuracy. The exceptionally low 9 V limit allows the transmitters to be used with low loop supply voltages, and it maximizes the voltage drop allowed in the current loop for intrinsic safety barriers and load resistance. For example, at the full 20 mA output of the transmitter, a 750 ohm load can be used with a 24 Vdc source and a 150 ohm load can be used with a 12 Vdc source. In either case, there will still be enough voltage left to power the transmitter, namely 9 Vdc.

10:1 Turndown Ratio
Turndown ratio is defined as zero suppression divided by span. The exceptionally high 10:1 turndown ratio possible with the 500 Series indicates that wide zero offset can be combined with narrow signal span for closed loop control at high gain. The signal span can also be wide for control of batch operations, where a wide range of signal levels may be encountered over the entire batch cycle.

High Overvoltage Protection
Overvoltage of 120 Vac may be applied across the input or output leads for 1 minute in case of all models with voltage or thermocouple input. Reverse polarity of 400 Vp may be applied across the output leads indefinitely. These exceptionally high NMV overvoltage ratings provide further protection against possible electrical faults and wiring errors.

DESIGNED FOR HARSH ENVIRONMENTS

Extreme Operating Temperatures
The operating temperature can be from -40░C to +85░C (-40░F to +185░F) while meeting published performance specifications. This allows the 500 Series to be used near furnaces or outdoors in the winter. The exceptionally wide operating temperature range is made possible by a proprietary electrical circuit and by extensive use of computer-graded and computer-matched electrical components.

Resistant to Shock and Vibration
The shock rating is 55 g, which includes a 6-foot drop onto concrete. This is made possible by a compact die-cast metal case, which is only 74 mm (2.9") in diameter, and by rugged mounting of the electronics. The circuit board assembly is in the shape of a rigid box and is firmly soldered to the top of the transmitter case.

Waterproof Case
The case is made of die-cast zinc alloy. It is waterproof to 35 kPa (5 PSI) and meets NEMA-4X standards. The top of the case is sealed against the bottom with a fluorosilicone gasket, and the openings in the top of the case for the zero and span adjustment are sealed with fluorosilicone plugs.

Explosion-proof Housing Options
Three external NEMA-7 explosion-proof and NEMA-4 waterproof enclosures are available as options for use in hazardous locations in Class I, Groups B, C, D; and Class II, Groups E, F, G. Option EPH1 is a single-height, all-metal housing for a single 500-Series transmitter. FM and CENELEC EEx d II C certification is standard. Option EPW2 is a double-height metal enclosure with a glass window for a 500-Series transmitter on the bottom and a 508B loop-powered indicator on top. FM and CENELEC EEx d II C certification is standard. The 508B augments the transmitter with an LCD digital readout scaled in engineering units and only adds a modest 2.5 V drop to the current loop. Option EPW3 is a single-height enclosure for one 508B loop-powered indicator. FM and CENELEC EEx d II C certification is standard.

EASY TO CALIBRATE AND INSTALL
There is no need to specify different models for different ranges of the same signal type. Zero and span are each set by push-on jumpers for coarse range selection and by a 15-turn precision potentiometer for fine adjustment. The two potentiometers are accessible from outside of the case through openings which are normally sealed by fluorosilicone plugs. To assist in calibration, two test terminals provide a 10 mV/mA output (200 mV full-scale). The scaling procedure is documented in a comprehensive userÆs manual, which is shipped with every unit.

Classical Application of a 500 Series 2-Wire Isolated Transmitter
The Transmitter amplifies a low-level voltage signal to 4-20 mA current signal, which is immune to voltage noise pick-up. The voltage detected in the control room is V = IR, where I is the loop current and R is the dropping resistor of the receiving equipment. The isolation provided by the transmitter protects the receiving equipment and eliminates the possibility of ground loops between the remote signal ground and the ground of the control room.