Page 6 • MNIN003 ║ Issue/Rev. 0.0 (5/19)
Percent Water Set Point
The Digital Indicator on the Model 4728 displays percent BS&W. The setpoint (BS&W
Limit) can be observed by moving the percent BS&W/Setpoint switch to the lower or
setpoint position. If it is desired to change the setpoint, rotate the setpoint adjust knob
until the new limit value is displayed. The switch must be held in the lower position while
performing this adjustment. When the switch is released the indicator will display the
percent water.
Time Delay
The delay that occurs between excess BS&W indication and bypassing, relay
transfer, is determined by the position of the time delay switch. The time is adjustable from
0-90 seconds in 10 second steps. The off delay, excess BS&W to merchantable oil, is
approximately 10 % of the on delay (30 sec. on, 3 sec. off).
Analog Output
The analog output is 4-20 milliamperes corresponding to 0-5%, 0-10%, 0-20% depending
on unit range. The 4-20 mA output function is accomplished by the use of a precision
integrated circuit. The 4 mA point may be adjusted slightly with the zero control on the
Model 4728. The 20 mA point is factory preset.
The Model 4728 utilizes a loop switch to determine whether the 4-20 mA loop will be
self powered or powered by a remote supply. In the internal mode the unit will drive
4-20 mA through a maximum loop resistance of 600 ohms. Loop resistance values of
>600 ohms are possible with an external power source.
In the external mode the current loop may be powered from an external power supply
(40 volts max.) through a 3 wire circuit. Maximum loop resistance will be
R loop = Vp - 13.5
.02
where Vp is the power supply voltage.
Note:
Under no condition should power be applied to the “+” or “-” 4-20 mA terminals.
Circuit damage will occur. See page 7 for hookup.
Installation
/
Operation
Manual
