Programming Point Types; Linear Current/Voltage Point Types; Deciding Which Voltage Range To Use; Current Inputs Voltage Shunt - Siemens SIREC D Handbuch

Programming

4.6.4 Programming Point Types.

There are various point types that can be selected,
from simple Linear to complex equations. Once a
point has been selected to Setup or Modify, the user
will be presented with the Point Type menu shown
in Figure 5-6. The various choices are:
•
Linear - Basic voltage and
current input with linear
scaling or dry contacts.
•
Industrial Square Root -
Performs square
extraction on input.
•
Log Linear - Performs
inverse logarithm on input.
•
T/c - Thermocouples as
defined.
•
Rtd - Resistance Temperature Devices as
defined (Option Required).
•
Calculated - Derived channels from user
entered algorithms.
•
Conditional - Boolean logic channels.
•
External - input channel via comm port.
At any point, if you exit the Points program-
ming menu after having made any changes,
(repeatedly pressing exit) you will be
prompted with a message "keep setup?". If
you select NO at this time, any changes you
have just made will be lost. If you choose
YES, the changes you made will be applied
to the point.
4.6.5 Linear Current/Voltage Point
Types.
The Recorder accepts two types of linear
current inputs: 4 to 20mA and 10 to 50mA and three
voltage ranges: ±100mV , +1 Volt +10 Volt. Dry
Contact will be covered later in this chapter.
A. 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).
4-22
Linear
Ind sqrt
Log Linear
T/c
Rtd
root
Calculated
Conditional
External
Figure 4-12 Point
Types Menu Box
NOTE
B. Current Inputs Voltage Shunt -
inputs are converted to voltage by means of an
external shunt resistor. The following formula is
used to determine the appropriate low and high end
input voltage:
Ohms Law: E = I * R
E = Equivalent voltage inputs
I = Current in milliamps
R = Precision shunt resistance value
1. Shunt Resistor Example - The following ex-
ample 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
1V 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, you can pro-
gram full scale ranges for the above input.
2. Programming Parameters - Once a point has
been programmed as Linear and a current or volt-
age mode selected, you are presented with the
menu shown in Figure 5-7 to program the pa-
rameters for:
•
Point Tag (up
characters)
•
Input Scale
•
Output Scale
•
Currents
•
Filter Seconds
•
Engineering Units (Up to
five characters)
•
Alarm Setpoints
Deadband, and Delay)
•
Chart Scale
Not all the above options will be available. It de-
pends on the choice of input range. Each of these
parameters is discussed in detail in the following
paragraphs.
Siemens AG C79000-G7374-C211-01
Current
Point Tag
to 10
Input scale
Output scale
Currents
Filter
Eng Units
Alarms
Chart scale
Figure 4-13 Point
Programming
Menu Box
(Limits,
SIREC D Manual