Dwyer 657-1, 657C-1 657-1 Manual

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Model 657 Relative Humidity/Temperature Transmitter

RECEIVER

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Specications - Installation and Operating Instructions

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The Dwyer Model 657 Relative Humidity/Temperature Transmitter provides two 4 to 20 mA channels to produce separate output signals for both relative humidity and temperature. This unit is housed in a compact ABS plastic case with screw-type

electrical connections. A separate 5/10˝ x 10˝ stainless steel sensing probe is factory

wired to the unit via a 48 inch (122 cm) cable. Sensor can be inserted directly into ducts

and secured by optional mounting kits A-158 or A-159. The A-158 kit is a split ange

with rubber gasket which is attached to a duct with sheet metal screws. The A-159 kit

has 1/2˝ NPT male threads which can be attached to sheet metal with washers and an included lock-nut or threaded into a standard pipe ange.

The sensor employed in the 657-1 features a state-of-the-art integrated polymer lm relative humidity sensor and a thin-lm platinum temperature sensor. These sensors

were designed to provide high reliability and stability over years of continuous service.

The relative humidity sensor uses a special polymer lm which absorbs water vapor at

a precisely known rate which is dependent on the relative humidity of the surrounding

air. This lm is deposited on a CMOS integrated circuit that measures and conditions the sensor output. The semiconductor and advanced lm technology ensure long

term stability and accuracy. The temperature sensor couples the highly accurate

and predictable temperature characteristics of platinum with a cost effective thin-lm

technology.

Installation

1. Location: Select a clean, dry location for the enclosure where the temperature

will not exceed the limits of 32 to 158°F (0 to 70°C). The transmitter can be

located any distance from the receiver provided the total loop resistance does

not exceed the limits as explained under “Wire Type and Length”. The probe

should be located where conditions are representative of the overall environment

being monitored. Avoid locations where stagnation or rapidly uctuating conditions might occur. Also avoid areas where water mist or condensation exist

which could cause erroneous full scale humidity readings.

2. Position: The probe and transmitter are not position sensitive and can be mounted in any orientation required.

3. Mounting: Using the through-holes in the transmitter body, attach the Model 657

to the mounting surface with two #6 machine or sheet metal screws of appropriate length. Avoid use of thread cutting screws which could produce metal chips which might cause a short if they enter the enclosure and thus damage the unit, Do not over-tighten screws to avoid damage to the case. To mount the probe, use either

the A-158 Split Flange or A-159 Duct Mounting Gland.

SPECIFICATIONS Relative Humidity Range: 0-100%. Accuracy: ±2% (10-90% RH), ±3% (0-10% and 90-100% RH). Operating Temperature Range: 32 to 158°F (0 to 70°C). Temperature Measurement Range: 32 to 212°F (0 to 100°C). Temperature Accuracy: ±1°F (0.5°C). Output: 2 channels, each 4 to 20 mA, loop powered on RH channel.

Power Supply: 10-35 VDC.

Ambient Operating Temperature Limits: 32 to 158°F (0 to 70°C). Storage Temperature Limits: -40 to 176°F (-40 to 80°C). Housing: ABS plastic. Sensor Probe: 5/16˝ x 10˝ (0.8 x 25.4 cm) stainless steel. Cable Length: 48 in (1.22 m).

Electrical Connection Caution: Do not exceed the specied supply voltage rating. Permanent damage, not

covered by warranty, may result. This unit is not designed for AC voltage operation.

Receiver-Transmitter Connection - The Model 657 transmitter is designed as a two-

wire 4 to 20 mA device with two channels. The channels are common on the negative

side of the current loops. Sensor excitation power is derived from the relative humidity

channel, so power must always be applied to that channel. If the temperature channel is not used, it can be left disconnected. The basic two-wire connection is shown in

Figure B. Terminal 4 can be used as a tie point since it is not used internally. However, the voltage on the terminal should not exceed the 35 VDC limit. Never connect AC or voltages exceeding 35 VDC to this terminal.

POWER SUPPLY

MODEL 657

RH/TEMP

TRANSMITTER

Figure B

RECEIVER

TEMPERATURE

DWYER INSTRUMENTS, INC.

P.O. BOX 373 • MICHIGAN CITY, INDIANA 46360, U.S.A.

Phone: 219/879-8000

Fax: 219/872-9057

www.dwyer-inst.com

e-mail: info@dwyermail.com

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Power Supply - The transmitter requires a minimum of 10 and a maximum of 35

VDC at its connection for proper operation. Choose a power supply with a voltage and

current rating which meets this requirement under all operating conditions. If the power supply is unregulated, make sure voltage remains within these limits under all power

line conditions. Ripple on the supply should not exceed 100 mV.

Loop Resistance - The maximum allowable loop resistance depends on the power supply voltage. Maximum loop voltage drop must not reduce the transmitter voltage below the 10 VDC minumum. Maximum loop resistance can be calculated with the following equation. VPS is the power supply voltage.

ps - 10.0

max =

20 mA

Some receivers, particularly loop powered indicators, may maintain a xed loop

voltage to power the device. This voltage drop must also be subtracted from the power supply voltage when calculating the voltage margin for the transmitter. The following

equation takes this into account. V

ps - 10.0 - Vrec

Rmax =

20 mA

rec is the receiver xed voltage.

To determine the maximum wire length, follow this procedure:

1. Determine whether the receiver is purely resistive or has a xed voltage drop,

then select the corresponding equation.

2. Determine the minimum power supply voltage that will be used. If the power supply is unregulated, use the voltage corresponding to the low-line condition.

3. Select the wire size and determine, from Table 1, the resistance per foot for that wire size. If the wire will be exposed to a wide temperature range, use the resistance corresponding to the highest expected temperature.

4. Calculate the maximum length. If the required distance is greater than the calculated value, choose a larger wire size and recalculate the maximum length.

Wire Resistance for Various Wire Sizes

AWG 16 18 20 22 24 26

Ohms/ft @ 32°F

.03983 .06332

.10069 .16010 .25459 .40486

Ohms/ft @ 68°F

.04495

.06873

.10928

.17375

.27628

.43930

Ohms/ft @ 122°F

.04833

.07684 .12218 .19426

.30886

.49114

Ohms/ft @ 167°F

.05256

.08360 .13291 .21132 .33596 .53445

Table 1

Wire Type and Length - Wire selection is often overlooked or neglected and thus can

contribute to improper or intermittent operation. Although 4 to 20 mA current loops are relatively immune to wiring related problems, for some systems, proper wiring can be an important factor in ensuring satisfactory system operation.

Twisted conductors are usually immune to most stray electric and magnetic elds, and to some extent electromagnetic elds such as interference from RF transmitters. Avoid use of at or ribbon cable which has no regular conductor twist. Where interference

is possible, use shielded wire. The shield must not be used as one of the conductors and should be connected to ground at one end only - generally at the power supply. Similarly, if the installation uses conduit, it should be connected to protective ground as dictated by applicable codes and the signal wiring must not be connected to the

conduit at more than one point or as specied by codes.

The maximum length of wire connecting the transmitter and receiver is a function of wire and receiver resistances. Wire resistance is negligible in most installations with shorter runs, typically under 100 feet. Generally, wire resistance should contribute no more than 10% to total loop resistance. Where long runs are necessary or unique application conditions exist, wire resistance must be carefully considered. Used the following equations to determine maximum wire length.

For a receiver with a pure resistive load, the maximum wire length is:

Lc max =

ps - 10 V - 0.2Rr

0.10Rco

For a receiver with a voltage drop specication, the maximum wire length is:

Lc max =

ps - 10 V - Vr

0.10Rco

Where:

c max = Maximum wire length in feet

ps = Minimum power supply voltage

r = Receiver resistance

r = Receiver voltage drop

co = Wire resistance per foot from Table 1

Multiple Receiver Installation

An advantage of the standard 4 to 20 mA DC output signal used in the Model 657

transmitter is the compatibility with a wide range of receivers. Devices such as the A-701, A-702 and A-705-20 digital readouts, chart recorders and other process control equipment can be easily connected and used simultaneously. It is only necessary that all devices be designed for standard 4 to 20 mA input, the proper polarity of input connections be observed and the combined receiver resistance or loop voltage not

exceed the maximum for the current loop. If any receiver indicates a negative or

downscale reading, the signal input leads are reversed.

MAINTENANCE

After nal installation of the Model 657 transmitter, no routine maintenance is required. These devices are not eld repairable and should be returned to the factory if recalibration or other service is required. After rst obtaining a Returned Good Authorization (RGA) number, send the material, freight prepaid, to the following address. Please include a clear description of the problem plus any application

information available.

Dwyer Instruments, Inc.

Attn: Repair Department 102 Highway 212 Michigan City, IN 46360

This symbol indicates waste electrical products should not be disposed

of with household waste. Please recycle where facilities exist. Check with your Local Authority or retailer for recycling advice.

This equation includes a 20% safety factor and accounts for the common lead carrying the current for both temperature and humidity channels.