7
Selecting the Number of Transducers
Next, we need to program the number of input channels and trans-
ducers (abbreviated XD in the displays and on the keyboard) that
will be recorded during the test.
Press
F3
to select the
#XDs
(number
of transducers) option in the test
setup menu.
The instrument prompts for the
number of transducers. The current
selection and default value is dis-
played within brackets.
For our example we will be using one
transducer. Key in 1 and press
EN-
TER
.
Our new data capacities are displayed
. . .
…and we are returned to the test
setup menu.
Defining Input Data Types
The last step in defining our test is to select the type of data to be
collected on each input channel. Selection of the data type will de-
termine both the measurement technique used to sample the trans-
ducer connected to an input and the equations used to convert the
measurement results to appropriate units.
Press
F4
to select the
TYPE
option in
the test setup menu.
We are presented with a menu of 4
data types. The type of data is inde-
pendently programmable for each
input channel. The current selection
is shown next to the input channel number.
Press
F3
to select the
FUNC
(func-
tion) option from the menu. The dis-
play will confirm your selection.
The function data type allows you to collect data from any 4-20 mA
transducer and convert the results to the desired units using a simple
linear or quadratic equation. The other data types provide more com-
plex data reduction features and will be discussed in later sections.
Press
CLEAR
to exit the data type
menu. Our new data capacities are
displayed . . .
. . . and we are returned to the test
setup menu.
Press
CLEAR
again to exit the test
setup menu and return to the
READY
display.
From this point on, all other functions and menu displays will be
automatically tailored to match your
SETUP TEST
selections. For
this reason it is important to configure the test using the
SETUP
TEST
function before attempting to alter other programmable set-
tings.
Setting Up the Inputs
Now that we have set up the basic test parameters, we need to pro-
gram the values that will determine how the 4-20 mA outputs of the
transducers will be converted to meaningful units.
If the HERMIT 2000 has dozed off,
press and release any key to wake it
up again.
Press the
XD
key to gain access to the trans-
ducer menus.
The transducer menu for input chan-
nel 1 is displayed along with a re-
minder that the input has been pro-
grammed as a function type.
Press
F4
to select the
more
option
from the menu. Additional menu
options for our function type input
are displayed.
The linearity (
LIN
), scale factor (
SCALE
), and offset (
OFFS
) pa-
rameters shown in the menu will program the coefficients of a qua-
dratic equation that will convert the transducer output to the desired
units. The values for these “Quadratic Coefficients” are generally
found on a data tag attached to the cable reel.
For purposes of this ex-
ample, our pressure trans-
ducer has a scale factor of
50.078 and an offset of
0.036. These values will
convert readings to PSI
units.
Section 2: Getting Started
Test 0: Setup menu
ALARM RATE #XDs TYPE
Number of XDs [4]?
_
Number of XDs [4]?
1_
Test 0: Setup menu
ALARM RATE #XDs TYPE
Input 1:
Level (F)
LEVEL FLOW FUNC DUAL
Input 1:
Function
LEVEL FLOW FUNC DUAL
DATA POINTS : 15558
Days at rate :
11
Test 0: Setup menu
ALARM RATE #XDs TYPE
READY
READY
Input 1: Function
READ I.D.
more
Input 1: Function
LIN SCALE OFFS DELAY
DATA POINTS : 15558
Days at rate :
11
Test 0: Setup menu
ALARM RATE #XDs TYPE
XD