Emerson Process Management 1500 manual •The mA output on Channel A can function as

Configuring the Filling and Dosing Application

Transmitter outputs change state according to fill status or operator commands. The control system opens or closes valves in response to the signals from the transmitter. The filling and dosing application must be configured for the type of valve used for fill control:

•One-stage discrete – Fill controlled by a single discrete (ON/OFF) valve. The valve opens completely when the fill begins, and closes completely when the fill target is reached (or the fill is paused or ended).

•Two-stage discrete – Fill controlled by two discrete valves: a primary valve and a secondary valve. One valve must open at the beginning of the fill; the other opens at a user-defined point. One valve must stay open until the end of the fill; the other closes at a user-defined point. See Figure 7-1for illustrations of the different opening and closing options.

•Three-position analog – Fill controlled by one analog valve which can be fully open, fully closed, or partially closed. See Figure 7-2for an illustration of the three-position analog fill.

The Model 1500 filling transmitter provides three outputs which can be used for valve control:

•Channel B always functions as a discrete output, and can be used to control the primary valve.

•Channel C can function as a discrete output or a discrete input. When used as a discrete output, it can be assigned to control the secondary valve.

•The mA output on Channel A can function as:

-A discrete output, to control either the primary or secondary valve. When used as a discrete output, an interposing solid-state relay is required.

-A three-level output, to control a three-position analog valve. When used as a three-level output, the 20 mA output level sets the valve to open full, and two user-specified output levels are used to set the valve to closed and to closed partial.

Note: If Channel A is configured for valve control, the channel cannot be used to report alarm status and the mA output will never go to fault levels.

Accordingly:

•A one-stage discrete fill requires either Channel A or Channel B configured to control the primary valve.

•A two-stage discrete fill requires any valid pair of Channels A, B, and C configured to control the primary and secondary valves.

•A three-position analog fill requires Channel A configured as a three-level output.

Note: See Table 7-1 for detailed information on output options.

54 Micro Motion® Model 1500 Transmitters with the Filling and Dosing Application