DRA-DCC-8 Calibration | Omega Vehicle Security instruction

The channel LEDs are connected in series with the output current so that they will light only as an indication of a closed current loop.

Note: After every power on, the unit is reset and the initialized default output currents are according to the SW6 setting (see para #5.2).

In the parallel control mode, internal pull-up resistors on each of the input terminals keep them in logical 1 state. The unit will recognize input voltage up to 0.5V as logical 0 and voltages from 4V to 60V as logical 1.

11. DRA-DCC-8 CALIBRATION

Generally there is no need to calibrate the DRA-DCC-8 unit. However if calibration is required, the following steps should be carried out: Two potentiometer trimmers, one for "Zero" and the other for "Span" are located on printed card 7040. The trimmer close to the card edge is the "Zero". Use the following switch setup for switching all the outputs between 4 and 20mA

MODE	S1	S2	S3	S4	S5	S6	S7
ALL CH. = 4mA	OFF	OFF	X	X	X	ON	OFF
ALL CH. = 20mA	OFF	ON	X	X	X	ON	OFF

Note: Set the unit to sink mode (fig.2).

Step 1:

Select one channel (for example ch.#1) for the initial tuning. Set the DIPswitch array to "all 4mA".

Apply supply voltage to the unit. The initial state of all the output currents is 4 mA. Use SW2 to switch all the outputs between 4 and 20mA. Iteratively set the "Zero" and the "Span" trimmers for 4.00mA and 20.00mA.

Step 2:

Monitor all the 8 channels in 4mA state, and calibrate the Zero trimmer so that their average readings is 4.000mA.

Then repeat for 20mA state, and calibrate the Span trimmer so that their average readings is 20.000mA. This procedure should be repeated until calibration is satisfactory.