Laurel Electronics LAUREATE SERIES DPM - Manual (Page 4)

1. INTRODUCTION
This series of panel instruments is a versatile, cost effective solution to a wide variety of
monitoring and control applications. These instruments are easily set to produce an
accurate display of temperature, pressure, flow, weight, voltage or current. Front panel
push-button or RS-232/RS-485 setup allows the user to customize the unit for a specific
application. Digital scaling of zero and span provides direct readout in engineering units.
Concurrent Slope ( Pat 5,262,780) is a new method of analog-to-digital conversion that
provides 60 conversions per second ( 50 for 50 Hz operation ) while integrating over a full
cycle of the line for maximum noise rejection. Self calibration cycles reduce the average
reading rate to 56 per second ( 47 for 50 Hz ). This fast read rate provides an accurate
display of peak signal input and quick response in control applications. The adaptive auto
filter automatically supplies a time constant compatible with the signal noise level. This
ensures stable displayed readings and outputs while responding rapidly to changes of the
input signal that exceed a selected threshold value. Selective security lockout of the front
panel setup protects against accidental changes to the meter. The instrument uses a
lightweight, high-efficiency switching power supply operating from AC or DC voltages.
The meter can be powered worldwide without changes to the supply. An optional low
voltage supply operates on 9 to 37 Vdc from batteries or 8 to 28 Vac from sources such
as 400 Hz aircraft power. Both supplies have isolated 5, 10, and 24 Vdc excitation outputs
to power transducers. The NEMA 4 (IP65) 1/8 DIN case is made of high impact, 94V-0
UL-rated plastic. Mounting is from the front of the panel and requires less than 110 mm
behind the panel. All wiring is by removable plugs conforming to IEC950 safety
standards. All output options are isolated from meter and power ground by 250 Vac
minimum.
The extended DPM is capable of linearizing a nonlinear input signal such as a thermistor,
gallons of liquid in a irregularly shaped tank, or altitude. Up to 240 points may be
linearized by a computer program that stores the parameters via RS232 into permanent
nonvolatile memory. The meter is also capable of measuring rate of change. The level
of a tank is measured and the difference between readings determines the flow rate in or
out of the tank.
The dual setpoints have two form C ( 10 A @ 250 Vac ) relays or solid state relay outputs
for alarm and control capabilities. Either setpoint may be latching or nonlatching and
separately configured to be energized above or below the setpoint, as deviation alarms,
or in a fail-safe mode. Additionally, outputs may also be selected to operate from the
filtered signal to reduce relay chatter or from the unfiltered signal for fast response.
Snubber circuits, programmable relay switching time delay and selectable hysteresis
extend relay contact life.
Isolation of the 4 to 20 mA and 0 to +10 V analog outputs eliminates ground loop problems.
The output may be scaled by front panel push-buttons or RS-232/RS-485. For thermo-
couples and RTD’s, the output is linearized. The 4 to 20 mA output will drive up to an 600
Ohm load with 12 V compliance
The meter offers RS232 or RS485 bidirectional communications or parallel, 3-state BCD
output to interface with computers, PLC’s or other digital devices. IBM PC compatible
software is available for programming the unit by the RS232 and RS-485 interfaces.
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