CJ1W-PH41U Universal Analogue Input Unit - User Range Setup
This tutorial supplements the Operation Manual (Ref W368-E1-__) describing how to set up User Ranges when using sensors that go outside the default setting range of 0.0C to 1000.0C.
Please make use of Manual W368 whilst reading this article.
By default, the PH41U unit range is set from 0.0C to 1000.0C. In most cases, users will find these settings adequate - e.g. for ovens, tempering, etc.
When using the default temperature range, the only setting required in the PH41U is to set the input type (e.g. PT100, K, T, etc) in Memory location (e.g. m+34 for sensor 1).
For example, if m+34 = 9, then this would set the sensor for Pt100-4wire. This sensor has a measurable range from -200C to 850C.
However, if no other settings are made then the measurable range at the PLC memory (n+0 & n+1) would be -150.0C to 1150.0C - not the expected -200.0C to 850.0C.Why is this?
This is because whilst the Sensor type is set in m+34, m+49, m+64 and m+79 (Sensor 1 to 4), the actual ranging is set according to values set in Process Value Input Range (m+35, m+36 for sensor 1, m+50 & 51 for sensor 2, etc) and also Process Value Scaling (m+39 to m+42 for sensor 1, m+54 to m+57 for sensor 2, etc).
By default the Process Value Input Range is from 0.0C to 1000.0C (0.1C setting) and the Process Value Scaling is also set to 0 to 10000. These settings imply a temperature range from 0.0C to 1000.0C.
The PH41U unit is able to read +/- 15% of Range, so actual readings would range from -150.0C to 1150.0C (15% of 1000 = 150).
An Example setting procedure to allow measuring the temperature of Liquid Nitrogen.
I want a Pt100 4-wire sensor to be able to measure the temperature of Liquid Nitrogen (-197C), with 2 decimal places of resolution.
Assume that the sensor is connected to Sensor 1 Input on PH41U.
Data Memory Settings would be:-
m+34 = 9 Pt100 4-wire sensor
m+35 = 8500 Input Signal maximum measurable value for Pt100 to 0.1C
m+36 = -2000 Input Signal minimum measurable value for Pt100 to 0.1C
m+39,40 = 85000 Value stored at maximum in Range - Span (850.00 to 2 decimal places)
m+41,42 = -20000 Value stored at minimum in Range -Zero (-200.00 to 2 decimal places)
Using Cx-Programmer's I/O table component, it is easy to set up the required ranges.
Note the Process Value from PH41U (as DINT) converted to ProcessValue_REAL with correct number of decimal places calculated from the Process Signal range and the Process Value range.
Should three (3) decimal places of accuracy are required, then the following settings would be required....
Giving the following output (via the FB again)...
The FB and sample code is included here as an attachment for download.