Bulletin A-33-A
page 3
2. Apply electrical power to the system and allow it to sta-
bilize for 10 minutes.
3. With no pressure applied to the transmitter, adjust “Zero”
control so that loop current is 4 mA.
4. Apply full scale pressure and adjust “Span” control so
that loop current is 20 mA.
5. Relieve pressure and allow transmitter to stabilize to 2
minutes.
6. Zero and Span controls are slightly interactive so repeat
steps 3 through 5 until zero and full scale pressures consis-
tently produce loop currents of 4 and 20 mA respectively.
7. Remove milliammeter from the current loop and proceed
with final installation of the transmitter and receiver.
WIRE LENGTH
The maximum length of wire connecting transmitter and
receiver is a function of wire size and receiver resistance.
Wiring should not contribute to more than 10% of receiver
resistance to total loop resistance. For extremely long runs
(over 1000 feet), choose receivers with higher resistance’s
to minimize size and cost of connecting leads. When the
wiring length is under 100 feet, lead wire as small as 22 awg
can be used.
MULTIPLE RECEIVER INSTALLATION
An advantage of the standard 4-20 mA DC output signal
provided by the 7000 Spirahelic
®
Pressure Indicating
Transmitter is that any number or receivers can be connect-
ed in series in the current loop. Thus, an A-701 digital read-
out, an analog panel meter, a chart recorder, process con-
trolling equipment, or any combination of these devices can
be operated simultaneously. It is necessary only that each
be equipped with a standard 4-20 mA input and proper
polarity of the input connections be observed when insert-
ing the device into the current loop. If any of the receiving
devices displays a negative or downscale reading this indi-
cates that the signal input leads are reversed.
MAINTENANCE
Upon final installation of the Series 7000 Spirahelic
®
Pressure Indicating Transmitter and the companion receiver,
no routine maintenance is required. A periodic check of the
system calibration is recommended. The Series 7000
Spirahelic
®
Pressure Indicating Transmitter is not field ser-
viceable and should be returned freight prepaid, to the fac-
tory (listed below) if repair is required (field repair should not
be attempted and may void warranty).
Dwyer Instruments, Inc.
Attn: Repair Department
102 Highway 212
Michigan City, IN 46360
A-33-A 4/16/03 10:33 AM Page 3
