Specifications

MFC-CB™ Operation and Maintenance Manual

5.2 VERIFICATION AND CALIBRATION OF ELECTRICAL

SIGNALS

5.2.1 PRINCIPLE

MFC-CB set and reads voltage and current values on two device channels (DEV1, DEV2).

The MFC-CB signals (each on 2 channels, DEVICE 1 and DEVICE 2) are:

• Set (V and mA): The electrical output. The “entered”, “displayed” or “nominal” set value

is the value input by the user and displayed on the MFC-CB front panel. The “actual” set

value is the value actually output by MFC-CB.

The “entered” and “actual” set values may differ due to the Sense adjustment.

The Sense line (see immediately below) measures the actual set output.

MFC-CB automatically adjusts the “actual” set value to make the Sense value agree with

the “entered” set value compensated by the K factor and adjustment factors when

applicable (see Section 7.1).

•

Sense (V): Measurement of the set output. The set output is adjusted automatically by

MFC-CB to cause the Sense to agree with the “entered” set.

• Measure (V and mA): Return from the MFC or MFM flow sensor.

• Valve (V): Direct measurement of the MFC internal valve voltage.

The MFC-CB measures voltage and uses on-board 5 and 10 V references to improve stability

over time. Voltage is converted to current using a precision 250 Ω resistor. The values of the

voltage references and resistor are determined and entered as part of the original factory

adjustment procedure and are accessible to DHI Authorized Service Providers only.

For calibration after the original factory calibration, each MFC-CB signal can be adjusted

mathematically using an adder and a multiplier. The normal procedure is to execute the

process automatically using CalTool for Analog software provided on the General

Accessories CD delivered with the MFC-CB and the special calibration cable included in

the accessories. See the CalTool for Analog User’s Manual on the General Accessories

CD for complete instructions. MFC-CB adders and multipliers can also be edited locally from

the front panel (see Section 5.2.2) or remotely (see Section 4.3).

See Section 7.2 for MFC-CB device channel connector pin outs.

CalTool for Analog and its User’s Manual are available for free download at