Doc#
M9344 • REV K
(April 2022) Page
2 of 8
INSTALLATION
1. MOUNTING
The transmitter body must be solidly mounted to the machine surface. See the section
Typical Transducer Placement. Different machine preparations are required for the two
basic transmitter mounting styles; NPT (National Pipe Thread) and machine thread (UNF and
Metric). Transmitters with the NPT type mounting stud are secured by the thread engage
-
ment and the base of the transmitter does not come in contact with the machine surface.
On the other hand, transmitters with the machine thread studs must make contact with the
machine surface. The transmitter base must make square and direct contact. This requires
preparing the surface of the machine with a 1 1/2 inch counter bore (surfacing tool). This
tool can be used with a portable drill equipped with a magnetic base take care such that the
tapped and threaded hole is perpendicular to the machined surface. The transmitter must
make contact all the way around its base surface. Contact Metrix for more detailed instruc
-
tions for using a counter bore.
If installing a transmitter with a standard 1/4 inch NPT stud, drill a hole using a 7/16 inch bit,
5/8 inch deep. Then tap using a 1/4 - 18 NPT (tapered pipe tap). Hand tighten the transmit
-
ter and then turn an additional 1 to 2 turns using a wrench on the wrench flats.
Do not use
a pipe wrench.
A pipe wrench can apply extreme forces to the body and potentially damage
electronic components. A minimum of five threads of engagement should be made. A 1/4
inch to 1/2 inch NPT bushing is available for mounting the transmitter in existing 1/2 inch NPT
holes. Also, a Metrix Model 7084 Flange Adapter can be used between the transmitter and
the machine surface when there is not enough surface thickness to drill and tap a hole. The
flange adaptor mounts with three small screws. See Accessories.
If installing a transmitter with one of the straight machined thread sizes, follow standard
drill and tap procedures. Be sure to not drill a hole larger that the counter bore pilot diam
-
eter before using the counter bore to prepare the machine surface. Drill out the hole with
the correct tap drill size after preparing the surface.
The sensitive axis of the transmitter is in line with the mounting stud. The transmitter can
be oriented in any (0 to 360 degree) position.
2. WIRING
The ST5491E is connected like any other loop powered transmitter. The following is a sum
-
mary based on area designations.
2.A SAFE AREA INSTALLATION
Connect the field wiring in accordance with the appropriate diagram on page 3. The ST5491E
transmitter requires a minimum of 13 VDC for proper operation. The minimum loop power
supply voltage required is 13 VDC plus 1 volt for each 50 ohms of loop resistance.
ST5491E Example:
Signal wire resistance
= 10
W
Resistance of receiver
= 250
W
Total loop resistance
= 260
W
Minimum supply voltage = 260
W
(1 VDC/50
W
) + 13 VDC = 18.2 VDC
