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17/64" Dia. Mtg. Holes (2)
Range Adjustment
Screw
1/2" NPT
Elect.
Conduit
Connection
1/8" NPT High
Pressure Port
1-11/16
[42.86]
1950G Switch Outline Dimensions
INSTALLATION
1.
Select a location free from excess vibration and corrosive
atmospheres where temperatures will be within the limits noted
under Physical Data on page 1. Switch may be installed outdoors
or in areas where the hazard of explosion exists. See page 1 for
specific types of hazardous service.
2. Mount standard switches with the diaphragm in a vertical plane
and with switch lettering and Dwyer nameplate in an upright posi-
tion. Some switches are position sensitive and may not reset
properly unless they are mounted with the diaphragm vertical.
3. Connect switch to source of pressure, vacuum or differential
pressure. Metal tubing with 1/4˝ O.D. is recommended, but any
tubing which will not restrict the air flow can be used. Connect to
the two 1/8˝ female NPT pressure ports as noted below.
A. Differential pressures - connect pipes or tubes from source
of greater pressure to high pressure port marked HIGH PRESS,
and from source of lower pressure to low pressure port marked
LOW PRESS.
B. Pressure only (above atmospheric pressure) - connect tube
from source of pressure to high pressure port. The low pres-
sure port is left open to atmosphere.
C. Vacuum only (below atmospheric pressure) - connect tube
from source of vacuum to low pressure port. The high pressure
port is left open to atmosphere.
4. To make electrical connections, remove the three hex head
screws from the cover and after loosening the fourth captive
screw, swing the cover aside. Electrical connections to the stan-
dard single pole, double throw relay and AC supply voltage con-
nections to the unit, are provided by means of terminals marked
"COM", "NO", "NC", "~" and "~" (See Fig. A). Electrical connec-
tions to the standard single pole, double throw relay and DC sup-
ply voltage connections to the unit, are provided by means of ter-
minals marked "COM", "NO", "NC", "+" and "-" (See Fig. B.). The
normally open contacts close and the normally closed contacts
open when pressure increases beyond the setpoint. Switch loads
for standard models should not exceed the maximum specified
current ratings as stated on page 1. For ATEX and IECEx compli-
ance, cables and cable glands suitable for temperature of at least
95°C shall be used. The cable entry device shall be of certified
flameproof type, suitable for the conditions of use and be correct-
ly installed. Refer to Certificate No.: IECEx TSA 08.0020X for con-
ditions of safe use for IECEx Compliant units. Switch capabilities
DWYER INSTRUMENTS, INC.
P.O. Box 373 • Michigan City, IN 46361-0373, U.S.A.
3-7/16
External
[87.31]
Ground
4-7/8
[123.8]
5-7/16
[138.1]
Vent
1/8" NPT
Drain
Low
Plug
Pressure Port
Captive
Screw
3/8
[9.525]
1-7/16
[36.51]
decrease with an increase in ambient temperature, load induc-
tance, or cycling rate.
ADJUSTMENT
To change setpoint:
A. Remove the plastic cap and turn the slotted Adjustment
Screw at the top of the housing clockwise to raise the setpoint
pressure and counter-clockwise to lower the setpoint. After cal-
ibration, replace the plastic cap and re-check the setpoint.
B. The recommended procedure for calibrating or checking
calibration is to use a "T" assembly with three rubber tubing
leads, all as short as possible and the entire assembly offering
minimum flow restriction. Run one lead to the pressure switch,
another to a manometer of known accuracy and appropriate
range, and apply pressure through the third tube. Make final
approach to the setpoint very slowly. Note that manometer and
pressure switch will have different response times due to differ-
ent internal volumes, lengths of tubing, fluid drainage, etc. Be
certain the switch is checked in the position it will assume in
use, (i.e. with diaphragm in a vertical plane) and switch lettering
and Dwyer nameplate in an upright position.
C. For highly critical applications check the setpoint adjustment
and if necessary, reset it as noted in step A.
MAINTENANCE
The moving parts of these switches need no maintenance or lubri-
cation. The only adjustment is that of the setpoint. Care should be
taken to keep the switch reasonably clean. Periodically the vent
drain plug should be rotated then returned to its original position.
This will dislodge deposits which could accumulate in applications
where there is excessive condensation within the switch. Repairs
to be conducted by Dwyer Instruments, Inc. Cover bolts are Class
10.9 35mm long.
Phone: 219/879-8000
Fax: 219/872-9057
Bulletin E-57G
Page 2
Fig. A
+
-
Fig. B
www.dwyer-inst.com
e-mail: info@dwyer-inst.com
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