Siemens SITRANS 7ME3500, Operating Instructions Manual, Page: 81 / 296

Connecting
5.5 Sensor Installation
FUE1010 IP65 NEMA 4X
Operating Instructions, 12/2014, A5E03086491-AC
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9. Rotate the track assemblies into their original position on the pipe. Use the edge of the
Mylar guide as a stop for both tracks and keep them parallel. Align each track with the
"center line" you previously marked on the Spacing Guide. Tighten tracks securely.
10.This time, before installing each sensor, apply a 3mm (1/8-inch) continuous bead of
couplant compound along the center (the long way) of the contact surface of the sensor.
Also, keep the sensors lifted slightly from the pipe when installing until the sensor is
against the pin; then push down against the pipe.
Note
Remember to install the sensors with the cable connectors facing away from each other.
11.Once the sensors are in place, secure with its clamping screws. Do not over tighten.
12.Observing the upstream and downstream orientation, attach the UP (upstream) and DN
(downstream) cables to the sensors and make snug. Attach the other ends to the UP and
DN terminals of the flow meter.
13.Proceed to Commissioning (Page 87).
5.5.6 Zero Flow Adjust Menu
Zero Flow Compensation Methods
Unlike turbine flow meters ultrasonic transit-time flow meters provide active flow
measurement right down to zero flow, however, the measurement of the transit-time delta is
dependent on the similarity or "match" of the electronics, cables and ultrasonic sensors.
Consequently some flow offset (or zero offset) may be present in any installation. To
eliminate this residual zero offset Siemens has developed several different methods to
insure proper zero flow compensation. The following paragraphs describe each method and
when they should be used.
AutoZero
When the 1011HP sensors are mounted in the Reflect Mode configuration the AutoZero
routine is automatically invoked at the end of the Initial Makeup. Flow does not have to be
stopped to perform AutoZero since only the pipe wall signal is used in determining the zero
offset and not the liquid component. The AutoZero routine performs a one-time analysis of
the pipe wall component of the ultrasound signal to quantify any residual mismatch in the
hardware. Once the AutoZero routine is complete, the system memorizes this measured
zero offset and subtracts this value from the flow reading.