|
| |
| Calibration
Methods for Process and Load meters |
| The Intuitive
offers you two methods of calibration, selected by rear switch position. |
- Direct Calibration, using an
input signal. Apply low then high input signals (the exact values of
which need not be known) and tell the meter what it should display
in both cases. This is quick and accurate, as all systems, sensor
and meter inaccuracies are compensated for during the calibration.
An example of using this method would be to have a weighing platform
with loadcells connected to the meter. You'd apply a known weight to
the platform and tell the meter what it should read, and then remove
the load and tell the meter to read zero.
- Theoretical Calibration. This
traditional method requires you to type in the low and high input
signal values, and low and high desired reading values. System
calibration inaccuracy depends on the sum of inaccuracies from the
sensor, plus transmitter (if used) plus meter, plus cable losses (if
applicable).
Top
|
| Automatic
Zero-Drift Compensation (Standard on -P and -L models) |
| In applications
where the meter normally reads zero (as in many weighing, pressure, or
QA testing applications) a feature exists to monitor and cancel any slow
drift caused by aging or thermal variations in the sensor and meter. The
meter always monitors its own reading, and, if it is in a small
percentage of range, near zero, it will assume that the reading should
be zero and will reset itself to show zero, without changing the full
scale sensitivity.
Top
|
| In-Flight
Compensation (Standard on all Intuitive meters fitted
with alarms) |
| If you enable
the in-flight compensation, the achievable precision in filling,
emptying or positioning applications may be greatly improved.
As an example, imagine a container,
filling with material which drops off a conveyor. The meter is set to
alarm when the container reaches its desired level, and will switch off
the drive motor. But after the alarm occurs, some material will still be
'in-flight' and the actual final weight will be a little more than
desired. The Intuitive meter will compare the setpoint level to the
final fill or empty weight, or position, shortly after the alarm occurs,
and will adjust for any error (overshoot) for the next filling,
emptying, or positioning operation. This is done each time, so if
material consistency varies and the in-flight error varies, the meter
will adapt.
Top
|
| 8
Program Memory (Optional on -P and -L meters) |
| With the MEM option, you can
store up to 8 sets of configuration and calibration data. This is useful
if you wish to connect a number of different sensors to the meter, each
with different calibrations. Each memory location may have its own
input/display calibration, alarm settings, and analog O/P calibration.
Memories are called up with an external
switch. If you need up to 4 memories, you may use a simple rotary
switch. If you need more than 4 memories, you'll need to use a BCD coded
switch.
The linearisation and theoretical
calibration facilities, remote tare, remote peak/valley and remote reset
aren't yet available with this option.
Top
|
| Display
Filtering (Standard on -P and -L meters) |
| A broad range of
signal filtering can be selected to reduce display jitter with noisy
signals. You can select time constants between 0.0 and 5.0 seconds.
Top
|
| Last
Digit Round-up (Standard on -P and -L meters) |
| You can select coarse display
resolution on the Intuitive-P and Intuitive-L models. The least
significant digits can increment in 1's, 2's, 5's, 10's, 20's or 50's.
This is useful if the displayed value is large and the resolution of the
system is poor. It reduces display jitter and drift, without reducing
conversion speed.
Top
|
| "So,
how do we calibrate a meter without using a menu system?" |
The Intuitive
meter family has a simple MENU-FREE calibration system. The most common
reason for customers seeking technical help after buying a programmable
meter is to ask for help with the menu. Engineers are busy, and can't
afford to spend much time learning complex menu structures.
So we created the simple Intuitive setup...
 |
Direct Access to:
Zero calibration
Span calibration
Decimal-point positioning
Alarm setting
Analog output calibration
Linearisation functions
|
Look at this photo of the Intuitive's
front panel. Imagine you want to adjust the ANALOG OUTPUT so that a
display of -40.0°C to +150°C gives 4-20mA output...
- Which button would you press to start
this process? Yes, the ANALOG O/P button! As soon as you press it,
the display shows a value and the 0% O/P light flashes. The value
shown is that which generates 0% output (or 4mA if you have the O/P
configured for 4-20mA). Well, we want 4mA to occur with a display of
-40.0 So using DIGIT, we move along each digit and amend with the UP
and DOWN arrows until the display shows -40.0. When it does we press
the OK button.
- Now, the display LED marked 100% O/P
flashes, with a new value. Again we move along each digit using the
DIGIT button and increase or decrease using the UP or DOWN buttons
until the display shows +150.0, pressing OK when done. That's it!
Notice we didn't step through other variables such as ZERO or SPAN
or ALARM settings to get to the variable we wanted. We went straight
to the ANALOG Output function.
- Imagine now, you want to set the
alarms, or adjust the Span, or the Zero...it's easy to see which
button you need to press, isn't it? And the adjustment system is
just the same...an LED illuminates to tell you which operation
you're performing, and you use DIGIT to select digits for altering
and UP/DOWN buttons to alter digits, pressing OK once your settings
are complete.
Top
|
|
"If
it's so easy, how do I stop my settings from being changed?"
|
There are two
scene methods of locking the meter, to prevent accidental or intentional
tampering.
- Lockout Switch. The lockout
switch is at the rear of the meter, so it is hidden when the unit is
installed in a panel.
- Plain Lens Substitute. After
you have adjusted the meter, you can unclip and replace the front
lens with a plain one, without pushbuttons. You must still activate
the lockout switch, for maximum protection and correct operation.
|
|
