Dwyer Instruments 490A Operating Manual

Series 490A Hydronic Differential Pressure Manometer

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Specications - Installation and Operating Instructions

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Bulletin D-24A

Series 490A Hydronic Differential Pressure Manometer are versatile, hand-held,
battery operated manometers available in several basic ranges for positive or positive
differential pressure measurement and can tolerate most liquid media compatible
with 316LSS. A memory function allows storage of up to 40 readings for later recall
and a backlight provides auxiliary lighting for hard-to-see locations. Standard are a
hold feature and both visual and audible overpressure alarms. A new feature added

to the Series 490A is a eld adjustable damping, independent viewable high/low

pressure readings, and low range increased resolution. This allows the user to choose

the level of display averaging rate corresponding to the uctuation level common in

many applications. A 9 V alkaline battery is included that provides up to 100 hours of
operation.

MODEL CHART
Model English Range Metric Range Maximum Pressure Available Engineering Units
490A-1
490A-2
490A-3
490A-4
490A-5
490A-6

0 to 15 psi
0 to 30 psi
0 to 50 psi
0 to 100 psi
0 to 500 psi
0 to 200 psi

0 to 103.4 kPa
0 to 206.9 kPa
0 to 344.8 kPa
0 to 689.5 kPa
0 to 3448 kPa
0 to 1379 kPa

30 psi (2.7 bar)
60 psi (4.13 bar)
100 psi (6.89 bar)
200 psi (13.78 bar)
1000 psi (68.9 bar)
400 psi (27.57 bar)

psi, in w.c., in Hg, cm w.c., mm Hg, kPa, hPa, mbar, bar, oz/in
psi, in w.c., in Hg, cm w.c., mm Hg, kPa, hPa, mbar, bar, oz/in
psi, in w.c., in Hg, cm w.c., mm Hg, kPa, hPa, mbar, bar, oz/in
psi, in w.c., in Hg, cm w.c., mm Hg, kPa, hPa, mbar, bar, oz/in
psi, in w.c., in Hg, cm w.c., mm Hg, kPa, hPa, mbar, bar, oz/in
psi, in w.c., in Hg, cm w.c., mm Hg, kPa, hPa, mbar, bar, oz/in

SPECIFICATIONS

Service: Compatible gases & liquids.
Wetted Materials: 316 SS; -3V option: 316LSS, Buna-N, silicone, grease, PTFE,

brass 360, copper, reinforced acetal copolymer; -HKIT option: 316LSS, PTFE,
brass, copper.
Accuracy: ±0.5% FS from 60 to 78°F (15.6 to 25.6°C); ±1.5% FS from 32 to 60°F
and 78 to 104°F (0 to 15.6°C and 25.6 to 40°C).

Pressure Hysteresis: ±0.1% FS.
Pressure Limits: See chart

Temperature Limits: Operating: 0 to 140°F (-17.8 to 60°C); Process with -HKIT
option: -20 to 180°F (-29 to 82°C); Storage: -4 to 176°F (-20 to 80°C).

Display: 4-digit LCD (.425˝ H x .234˝ W digits).
Resolution: See chart.
Process Connections: Two 1/8˝ (3.18 mm) female NPT; -HKIT option: Two 1/4˝

male 45° are ttings.

Power Requirements: 9 V alkaline battery, installed non-functional, user
replaceable.

Weight: 14.1 oz (400 g); -HKIT option: 3.6 lb (1.63 kg).
Agency Approvals: CE.

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DWYER INSTRUMENTS, INC.

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

Phone: [phone]

Fax: [phone]

www.dwyer-inst.com

e-mail: [e-mail]

BATTERY INSTALLATION

The unit is shipped with a separate 9 volt alkaline battery which must be installed
before operation. Remove the two screws holding the bottom endcap in place and
remove the endcap. Connect the battery to the enclosed battery clip, making sure to
observe correct polarity. Be careful not to trap wires between the battery, case, or foam

pads which retain the battery. This could make it difcult to install the battery or remove

it later for replacement. Be sure that the rubber gasket is properly seated in the gasket

channel of the endcap and replace endcap. Note that the endcap will only t one way

because the holes are slightly off-center. Place the Z shaped wrist strap clip in one of
the screw recesses and replace the screws. Do not over tighten the screws. Attach
the wrist strap to the clip. Note: On –HKIT option 490A, the rubber boot will have to be
pulled back to have access to the battery compartment.

When battery replacement becomes necessary, use only a 9 volt alkaline type such as

a Duracell

®

MN 1604, Eveready® 522, or equivalent. Zinc-carbon types, often labeled
heavy-duty are not recommended because of the increased potential for leakage.
Alkaline batteries are also a better value because they last up to three times longer
in this device.

Low Battery Indicator

A weak battery can cause improper operation or inaccurate measurements. A
low battery indicator is provided on the display to show when the battery needs
replacement.

NOTICE

Although the unit might appear to function and indicate properly,

the accuracy of readings cannot be guaranteed when the LOW

BAT indicator is illuminated. Replace the battery with a new one. Do not leave an
exhausted battery in the unit due to potential leakage.

ON-OFF OPERATION

Press the ON/OFF button once to turn the unit on. Once on, press the ON/OFF button

for more than 5 seconds to turn the unit off. If the manometer is left on with no activity
for approximately 20 minutes, the unit will turn itself off to conserve the battery.

ZEROING PRESSURE READING

Potential inaccuracy due to temperature effects can be minimized by re-zeroing
immediately before use. To zero the display, vent both ports to the atmosphere so

no pressure is applied to either port. Press the ZERO/STORE button and ---- will be

momentarily displayed as zeroing occurs. Zeroing is not possible when the memory
mode is in use. It must be done before selecting that function.

If the unit is accidentally zeroed with pressure applied to one of the ports, the pressure
reading might display incorrectly. To correct, vent the pressure ports to atmosphere

and press the ZERO/STORE button to zero the unit.

BACKLIGHT

The Model 490A includes a display backlight to allow use in the dark or in poor lighting

conditions. Pressing the ON/OFF button toggles the backlight on or off. With the 490A
on, press the ON/OFF button to toggle the backlight on or off. The backlight will remain

lit for approximately 2 minutes after which it will turn itself off to conserve battery life.

AUTOMATIC RESOLUTION ADJUSTMENT

For all ranges, the series 490A will automatically move the decimal place one point to
the left when reading in the bottom 10% of its calibrated range. This allows the user
to gain a higher resolution reading for lower static or differential pressure readings.

SELECTING PRESSURE UNITS

Up to seven pressure units are available. The display will indicate the current

selection. To change to different units, use the UNITS/LOC button. Each press of the

button will cause an advance to the next choice. The selected units will remain in the
memory even when the power is shut off. This way, the user preferences will always
be displayed after the initial selection.

DISPLAY HOLD

In situations where a reading needs to be temporarily retained, the Model 490A
includes a display hold feature which freezes the current reading and holds it on the

display until it is cleared. To activate this operation, press the HOLD/MEMORY button

when the desired pressure is displayed. A HOLD indicator will appear on the display
to indicate that the reading shown is frozen. To return to normal operation, press the

HOLD/MEMORY button again. The HOLD indicator will disappear and the current

pressure will be shown.

MEMORY FUNCTION

A memory function is included in the Model 490A that allows users to store up to 40
pressure readings for later review or recording. The readings are stored in non-volatile
memory so they will be retained even if the unit is shut off or the battery is removed.

Storing Pressure Readings

To store a reading, press and hold the HOLD/MEMORY button until ST01 displayed.
Next, press the ZERO/STORE button to safe the current reading to the ST01 memory

location. A beep will sound indicating that the reading has been saved. As each
reading is saved, the memory location display will advance to the next number. To

resume pressure measurement, press the HOLD/MEMORY button again. Note that in

the memory mode, the display zero function is not available. To zero the display, exit

the memory mode and then press the ZERO/STORE button.

Viewing Stored Readings – Selecting a Location

To view the contents of the memory, press and hold the HOLD/MEMORY button
until RD01 is displayed. Next, press UNITS/LOC to view other memory locations. To
resume pressure measurement, press the HOLD/MEMORY button again.

Clearing Memory

To clear the contents of the memory, press and hold the HOLD/MEMORY button until
CLR is displayed. Next, press the ZERO/STORE button to clear all previously stored

readings. During this operation --- will be displayed. Once the memory is cleared, the
current pressure will be displayed.

Exiting Memory Mode

To exit the memory mode, press the HOLD/MEMORY button again and the unit will

return to normal operation.

PRESSURE CONNECTION

Measuring Single Pressure

To measure single positive pressure, connect the tubing to the port marked “High
Pressure” and vent the opposite port to the atmosphere.

Measuring Differential Pressure

To measure differential pressure, connect the higher positive pressure to the port
marked “High Pressure” and the lower positive pressure to the port marked “Low
Pressure”. The manometer will indicate the difference between the two.

Overpressure Alarm

A visual indicator and audible alarm are provided to alert the user that pressure has
exceeded the operating range of the unit. Exceeding the range will not damage it
or affect calibration as long as the maximum rated pressure is not exceeded. The
maximum pressure for all units is shown on the rear label and on page 1 of these
instructions.

CAUTION

Do not exceed the maximum rated pressure of the manometer.
Doing so will cause permanent damage to the sensor, may rupture

the housing, and/or cause personal injury.