Endress+Hauser promag 30, Operating Manual

Page: 36 / 72

➤
Setting the full-scale value
Works setting: at v ~ 2.5 m/s
Switches No. 8, 9, 10: OFF-OFF-ON
The current output supplies signals between 0/4 and 20 mA, corresponding to the
momentary value of the flow. By setting the full-scale, a flow is assigned to the current
of 20 mA. This setting always applies to both directions of flow (bidirectional). The
direction of flow is emitted at the status output with appropriate configuration.
In practice the maximum rate of flow that occurs is not always reliably known.
Therefore it is possible to extend up to 125% (500 Hz, see Fig. 38).
For the Promag 30 measuring system eight preset pulse-value steps can be selected
in terms of the nominal diameter. Setting is made by means of three miniature
switches (see page 37).
➤
Auxiliary input
The auxiliary input cannot be affected
by the miniature switches
•
Measured value suppression:
With the auxiliary input it is possible to keep a check on the behaviour of the current
and pulse outputs by means of an external voltage (3...30 V DC). Provided this
voltage is applied, the current is set to 0 or 4 mA and the pulse output to the
fallback value (transistor not conducting).
Typical application: Interrupting measurement to clean the piping system.
•
Totaliser reset:
The auxiliary input can also be configured as an external reset for the totaliser using
a jumper (only with local display, see page 42, 43).
➤
Electrode Cleaning Circuit ECC (Option)
Conductive material build-up on the electrodes (e.g. magnetite) can lead to errors in
measurement. The electrode cleaning circuit (ECC) has, therefore, been developed to
prevent such a build-up. The cleaning cycles are carried out every 30 minutes for
2...5 secs each depending on the scanning frequency. If the Promag 30 measuring
system is equipped with the electrode cleaning circuit option (ECC), then this can be
switched on and off using the miniature switches on the amplifier board (see Fig. 44,
on page 48). When delivered from the factory, the electrode cleaning circuit is always
switched on. The ECC is not available with the FL version.
Caution!
If the ECC is switched off for a long period of time in an application with conductive
build-up, then material build-up in the measuring pipe can lead to measuring errors.
If there is a large concentration of build-up at one point, then, under certain
circumstances, switching on the ECC may not remove it. In such cases the measuring
pipe is to be cleaned and the build-up removed.
500 Hz
ba00
8y
3
5
Measuring range for Promag 30 electronics
Flow rate Q ~ Medium velocity v
Maximum
full-scale value
20 mA current
Minimum
full-scale value
0 0.5 10
12.5 [m/s]
Fig. 38
5. Operation and Commissioning Promag 30
36 Hauser