This document describes how to calculate a counter scale factor.
Many Red Lion Controls counters have the ability to scale the input signal in order to obtain the desired display value. This is accomplished by using the counter's scale factor. It could be used, for example, with a length sensor to display length such as feet or meters. Another common application is rate, RPM, FPM, etc.
APPLICABLE PRODUCTS
PAXC0020, PAXC0030, PAXI0020, PAXI0030, PAXLCR00, PAXLCRU0, PAXR0020, PAXR0030
PRE-REQUISITES
- For length applications, have your encoder pulse rate
- For rate applications, like RPM, FPM, etc. Have your pulses per engineering unit.
IN THIS ARTICLE
Method 1: Known Pulses per Unit
First, determine where you want the decimal point to be located.
0=1
0.0=10
0.00=100
0.000=1000
0.0000=10000
Now determine the number of pulses the counter will receive per engineering unit.
Engineering Unit – The units being represented on the display. For example, for a distance measurement application, the displayed engineering units may be in feet, inches, miles, etc.
To determine the scale factor, divide the desired decimal point location number by the number of pulses per engineering unit.
Example:
If you want to display 2 decimal positions (0.00) and you have 200 pulses per unit. Your scale factor would be 100/200=0.5
Method 2: Unknown Pulses per Unit
Start by programming the display decimal place to 0, and set the scale factor to 1.000
Reset the counter to 0, and run a known length of material, until the desired unit has been achieved.
For example, if you have an application measuring feet, run the application until 1 foot has been measured.
The number that is displayed on the counter will be your pulses per unit because the scale factor has been set to 1.00, the decimal position was 0.
Now calculate the scale factor using the formula described below.
The meter is to display feet to 1/10th decimal place. After a distance of 1 foot has been traveled. The number of input pulses per foot will be displayed. For feet to 1/10th decimal position, take 10 divided by your displayed pulse value. To program the meter, set the display decimal position to 0.0. The counter scale factor to the example value below.
One foot of travel = 500 display pulses
Calculated scale factor is 10/500= 0.02000
Method 3: Rate Scaling
When scaling a panel, meter to display rate. You, generally, only need to know two values
- Display unit time base, per second, minute, hour.
- Number of input pulses per engineering unit.
Example. Programming the PAXI panel meter for RPM, with 60 input pulses per rotation of a gear.
In menu 4-RTE
Program the rDSP 1 value at 60. This is based on 60 seconds in a minute.
Program the rINP 1 value at 60. This is based on the number of input pulses per unit.
If your displayed time base is per second, hour, or if the input pulse rate is less than 10 pulses per unit. Reference page 18 of the Product manual for more scaling instructions.
Additional Info