Linear Current/Voltage Point Types; Dry Contact Point Type - Omega RD8800 User Manual

Chapter 5 Programming

5.6.6 Linear Current/Voltage Point Types

The Recorder accepts five types of voltage linear inputs: 150mV, 1.25V, 2.5V, 12.5V and 25V and three types
of linear current inputs: 4 to 20mA, 0 to 20mA and 10 to 50mA.
NOTE: The Dry contact Point Type is described in Section 5.6.7.
Deciding Which Voltage Range to Use - In deciding which of the voltage ranges to use, select the smallest
range that will accommodate the full span of the input signal for the best resolution and accuracy of the Analog-
to-Digital Converter (ADC).
Current Inputs Voltage Shunt - Current inputs are converted to voltage by means of an external 50 ohm shunt
resistor supplied by the user. The following formula is used to determine the appropriate low and high end input
voltage for non-standard current inputs:
Ohms Law: E = I * R
E = Equivalent voltage inputs
I = Current in milliamps
R = Precision shunt resistance value
Shunt Resistor Example - The following example shows a low and high end input voltage for a 0 to 1mA input
with a precision shunt resistance of 1000 ohms with the measurement done on the 1.25V range.
E = 0 x 1000 = 0mV = 0 V (Low input)
E = 1 x 1000 = 1000mV = 1 V (High input)
Using the Input and Output scaling, the user can program full scale ranges for the above input.
Programming Parameters - Once a point has been programmed as Linear and a voltage or current mode is
selected, the user is presented with the following parameters:
Point tag
Input scale
Output scale
Exc. Currents
Filter
Eng units
Alarms
Chart scale
Output mode
NOTE: Not all the above options will be available. It depends on the choice of input range.

5.6.7 Dry Contact Point Type

The Dry contact Point Type allows a point to be programmed to act like an open or closed contact. The input
can be a set of potential free contacts. Logically an open contact is equal to 0 (zero) and a closed contact is
equal to 1.
Once a point has been programmed as Linear-Dry contact the user is presented with the following parameters:
Point tag
Eng units
Alarms
Chart scale
Artisan Scientific - Quality Instrumentation ... Guaranteed | (888) 88-SOURCE | www.artisan-scientific.com
Section 5.6.5.1
Section 5.6.5.2
Section 5.6.5.3
Section 5.6.5.4
Section 5.6.5.6
Section 5.6.5.9
Section 5.6.5.10
Section 5.6.5.11
Section 5.6.5.12
Section 5.6.5.1
Section 5.6.5.9
Section 5.6.5.10
Section 5.6.5.11
Page 5-24