Siemens 7ML19985AB01 instruction manual Fail-Safe, Flow Rate and Totalizing, Flow rate

The mA function can be overridden for test purposes by setting the desired mA value into F3. When the value is entered, the mA output will go to that value. When F3 is exited, the mA output will revert to normal operation. Also, see \ Emulation Mode.

*In the case of absolute calculations (P4=0), P6 is calculated by the OCM-3.

FAIL-SAFE

In the event of an echo loss, the fail-safe timer will begin counting. If the echo loss duration surpasses that of the time set (P29), a ‘No Echo’ alert will be displayed in the Status field (see \ Display). The mA output will respond (P30) by either holding the last value or immediately going to a predetermined value (P31). The head and derived flow will hold their last value and totalization and logging will continue, based on that value. Upon resumption of a valid echo, the mA output will return to a value corresponding to the present value of the measurement assigned, at the mA damping rate (P27).

FLOW RATE AND TOTALIZING

Flow rate

Calculation of the flow rate is ongoing. It is normally viewed under the Flow and Total display (F2) with the decimal point set per P33. It can also be viewed under D1 as the raw flow calculation. Data on the running minimum and maximum flows that have occurred since the last reset can be viewed in two ways:

»F7 gives the running min/max flows and their time and date of occurrence since the last reset. F7 is reset by F8 but only after satisfying the security parameter F0.

»D3/D4 give the respective running min/max flow data, only, that have occurred since they were last reset. D3/D4 are reset simultaneously by entering 0 into either D3 or D4. D3 and D4 will then adopt the current flow rate and track the running min/max values from that point on. The security parameter (F0) does not need to be satisfied in order to reset D3/D4.

Flow data specific to a particular time and date can be viewed under the data log F14 (see \ Logging).

Totalizing

Totalizing of the calculated flow is ongoing. It is normally viewed under the Flow and Total display (F2).

An auxiliary totalizer (D2) is provided for operator usage and is intended for short term totalizing to a maximum count of 999999. It can be reset or preset independently of the F2 totalizer after satisfying the security parameter (F0).

In order to adjust the rate of filling of the totalizer, the totalizer multiplier (P32) can be set to an appropriate value. The totalizer can be reset via F11. Totalizing that is specific to the time and date can be viewed under the data log F14.

The OCM-3 can be programmed to operate a remote totalizer by assigning any of the relays (P15, 18 or 21) to act as a totalizer contact*. Under this function, the maximum rate of contact closure is 2/sec with a closure duration of 200 msec**.

*The totalizer count is set by the relay setpoint parameter (P16, 19 or 22 respectively).

**Typically the totalizer should be set for 300 to 3000 counts per day at maximum flow.

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