1.0 GENERAL INFORMATION
The
501 two-wire transmitter supplies a 200-microampere current to
the Pt-100 RTD, gauges the resulting microvolts, and provides
amplification and common-mode isolation, controlling the current
drawn from a 9-to-50 V dc source to produce the 4-to-20 milliampere
output signal.
Common-mode voltage between the input RTD and the output current
circuit is tested at 1500 V rms. As much as 750 ohms dropping
resistance may be used in the power leads of the 501 when the
unit is energized from a 24 V dc source because of the small compliance
voltage needed by the unit. Accidental overloads of over one minute
by 120 V rms on the output leads do not damage the 501.
1.1 ACCURACY AND STABILITY
The 501 has tailored resistance values installed to
provide low temperature coefficients and a high degree of lead-resistance-effect
rejection in 3 (or 4) -wire configurations. Selected bridge resistors
in a temperature-sensing bridge provide cancellation of Span temperature
effects. High-ambient-temperature compensation points are checked.
The unit is certified for accuracy from -40 to +85°C (-40
to +185°F).
1.2 ADAPTABILITY/TURNDOWN
The
Span of the 501 can be ranged anywhere from 100 to 1050°C
by selection of four jumper positions, with fine tuning provided
by a multiturn, top-accessible potentiometer. Sixteen Zero steps,
also provided by 501 jumpers, allow placement of the 4-mA output
temperature anywhere from -200 to 750°C, with fine tuning
provided by another top-accessible, multiturn potentiometer. This
501 turndown capability exceeds that of any other known RTD transmitter.
1.3 LINEARITY
The span and zero suppression capabilities (high turndown ratio)
allow high-gain control for continuous processes and good linearity
over narrow temperature ranges. Downstream linearization of the
4-20 mA signal is required for accurate absolute temperature readout
over a wide span.
1.4 ELECTRICAL ISOLATION
501 input (2, 3 or 4-wire RTD) and output (DC power)
barrier strips accept wires up to 2 mm diameter (13 gauge), and
are mechanically isolated from each other to prevent input/output
wiring contact during installation.
1.5 SHOCK RESISTANCE
Lightweight 501 circuit boards are formed into a rigid
box structure and firmly soldered to the case top. The circuit-board
box is doubly coated with RTV silicone for environmental protection.
When installed in the rugged, die-cast case, the 501 can withstand
the shock of a 6-foot drop onto a hard surface (although scarring
of the case and/or deformation of the plastic cover can occur).
1.6 WATERPROOF/RFI-RESISTANT CASE
The 501 case is made from Zamac (zinc alloy), coated
with polyurethane, and gasketed with fluorosilicone. Fluorosilicone
plugs protect the top-access Span and Zero potentiometers.
1.7 MOUNTING ADAPTABILITY
The small size of the 501 (less than 75 mm or 3 in
OD) permits mounting in small spaces, including explosion-proof
housings for wiring compatability with other equipment in hazardous
environments. A bulkhead adaptor provides for wall-mounting. A
snaptrack adaptor mounts on either American or European relay
tracks. Tapped holes in the case rear provide for custom mounting
on any surface, indoor or out. An optional opaque top cover shields
the barrier strips from harsh environments.
2.0 SPECIFICATIONS
2.1 INPUT
Configuration:
Isolated input
Sensor types: 2, 3 or 4-wire RTD probe or variable resistor
(from 0 to 400 ohms, minimum span of 35 ohms)
Input current source: 200 mA nominal
RTD lead resistance rejection: 40 dB (balanced 3-wire)
Common mode voltage, input to case: Test, 2100 V peak;
IEC spacing for over 354 V peak
Common mode rejection, input to case: 120 dB, dc to
60 Hz
2.2 OUTPUT
Linear
range: 4 to 20 mA dc
Compliance (supply-voltage range): 9 to 50 V dc
Overvoltage protection: 120 V ac for 1 minute
Reverse polarity protection: 400 V peak
Common mode voltage, output to case: 1500 Vp (354 Vp
per IEC spacing)
Common mode rejection, output to case: 120 dB, dc to
60 Hz
2.3 ACCURACY
Hysteresis
and repeatability: Within ±0.2°C ±0.1% of span
Six month stability: Within ±0.2°C ±0.2% of base
temp
Power supply effect: Within 0.01% of span/volt
Ambient temperature effect:
Zero
Error: ±0.04 °C/°C Typical
Span: ±0.03 °C/°C Typical
2.4 ENVIRONMENTAL
Operating
temperature: -40º to 85°C
Storage temperature: -55 to 125°C
Humidity: To 100% (splashproof)
Vibration: 1.52 mm (.06 in) double amplitude, 10-80
Hz cycled
Shock: 55g, half-sine, 9-13 msec duration, 6' drop
to hard surface
Watertight pressure limit: 35 kPa (5 psi)
Mounting position: Any
2.5 MECHANICAL
Case
material: Zamac (zinc alloy), polyurethane-coated, fluorosilicone-gasketed
Weight: 380 g (13 oz)
Diameter: 74 mm (2.9 in)
Height (including barriers): 52 mm (2.1 in)
Connections: #6 screws with wire clamps
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