IRROMETER RSU-C Installation And Operating Instructions Manual

— CAUTION —

Do Not Install by Hand

You must use a wrench on the brass fitting

(9/16" wrench for the 1/4" transducer or 1/2" wrench for the 1/8" transducer)

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Model RSU-C

INSTALLATION AND OPERATING INSTRUCTIONS

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RSU-C – Remote Sensing Tensiometer

The IRROMETER RSU-C incorporates a pressure
transducer and electronics in a potted waterproof
housing. The RSU-C can be installed in the gauge
port of any IRROMETER, thus converting the reading
to a 4-20 ma loop current signal. It can be interfaced
with a 4-20 ma loop current terminal or to an A/D card
designed to read voltage. Excitation current required
is 12 – 24 VDC.

The RSU-C is available in two different calibrations:

Standard Instruments (RSU-C-93)

4-20mA = 0-93 kPa (0.172 mA per kPa)

Low Tension Instruments (RSU-C-34)

4-20mA = 0-34 kPa (0.471 mA per kPa)

Note 1: Connection size must be specified when ordering RSU-C only: 1/4'' MNPT or 1/8'' MNPT.
Note 2: Two wire insulated cable (suitable for direct burial) should be used to connect RSU-C to

Electronic Reading Device – #18 AWG size (standard preferred).
For devices that cannot read a current loop but can read a voltage, a resistor can be used to

translate the current loop into a voltage. A 250 ohm resistor will convert the 4-20mA output into a
1V to 5V reading. The following figure illustrates this configuration:

Figure 1

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— WARNING —

Do Not use water containing chlorine or sulfur (distilled preferred)
or cleaners containing chlorine or sulfur with the RSU-C.

When de-airing the transducer equipped IRROMETER (Model RSU-C)
care must be taken to release the vacuum slowly. A sudden release
of the vacuum could cause damage to the pressure transducer,
rendering the instrument inoperable. Transducers damaged by
sudden release of the vacuum are unrepairable and would require
complete replacement of the entire transducer assembly.

3

Reading the RSU-C with a Digital Meter

VACUUM

0 kPa

50 kPa

93 kPa

0 kPa

17 kPa

34 kPa

RSU-C-93 (Standard Instruments)

The DVM shows 4mA

The DVM shows 12.6mA

The DVM shows 20mA

RSU-C-34 (Low Tension Instruments)

The DVM shows 4mA

The DVM shows 12mA

The DVM shows 20mA

(4/16) #731

LITHO U.S.A.

Optimizing Irrigation . . .

Maximizing Conservation . . .

Worldwide Since 1951

WARRANTY: The IRROMETER COMPANY warrants its products against defective
workmanship or materials under normal use for one year from date of purchase. Defective parts
will be replaced at no charge for either labor or parts if returned to the manufacturer during the
warranty period. The seller’s or manufacturer’s only obligation shall be to replace the defective
part and neither seller nor manufacturer shall be liable for any injury, loss or damage, direct or
consequential, arising out of the use of or inability to use the product. This warranty does not
protect against abuse, shipping damage, neglect, tampering or vandalism, freezing or other
damage whether intentionally or inadvertently caused by the user.

®

1425 Palmyrita Ave., Riverside, CA 92507

951-682-9505 • FAX [phone]

[e-mail]

www.IRROMETER.com