Dwyer 490 - Manual (Page 2)

INSTRUCTIONS
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 observing correct polarity. Be careful not to trap wires between
the battery, case or foam pads which retain the battery. This could make it difficult to install the battery
or remove it later for replacement. Be sure the rubber gasket is properly seated in the gasket channel
of the endcap and replace endcap. Note that the endcap will only fit 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 overtighten the screws. Attach wrist strap to clip.
When battery replacement becomes necessary, use only a 9 volt alkaline type such as a Duracell ®
MN1604, 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.
On-Off Operation
The on-off control is a toggle function. Press and release the ON/OFF key once to turn unit on;
again to turn it off. If the manometer is left on with no activity for approximately 20 minutes, unit will
turn itself off to conserve the battery.
Display Backlight
The Model 490 includes a display backlight to allow use in the dark or in poor lighting conditions.
Manometer must be switched off before this feature can be activated. Next, press and hold the
ON/OFF key down. After about 1 second the backlight will come on and remain lighted for
approximately 2 minutes after which it will turn itself off to conserve battery life.
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 atmosphere so no pressure is applied to either
port. Press the ZERO/STORE key 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 key to zero the unit.
Pressure Connections
Dual 1/8≤ female NPT connections are provided. For a single positive pressure, connect tubing
to port marked + and vent opposite port to atmosphere. To measure differential positive pressure,
connect higher positive pressure to port marked + and lower positive pressure to port marked -.
Manometer will indicate the difference between the two.
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 key. Each touch will cause an advance to the next choice. The
selected units will remain in memory even when power is shut off. This way, your preference will
always be displayed after the initial selection.
Display Hold
There may be situations where you want to temporarily retain a reading. The Model 490 includes
a Display Hold feature which freezes the current reading and holds it in the display until cleared. To
activate this operation, momentarily press the HOLD/MEMORY key when the pressure you want to
save is displayed. A HOLD indicator will appear in the display to indicate that the reading shown is
frozen. To return to normal operation, press the HOLD/MEMORY key again.The HOLD indicator will
disappear and the current pressure will again be shown.
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