iRIS 220 / iRIS 320, V1.19 User Guide - 60
7 Analogue Input Scaling
This section explains the recommended procedure to use when scaling an analogue input (voltage or current). It makes use of the scaling calculator provided in the iLink utility. However, the calculation can be done manually using this formula. NOTE: mV = Input mV, EU = Engineering Units (scaled output e.g metres)
Multiplier = (Maximum EU – Minimum EU) / (Maximum mV – Mi nimum mV)
Offset = Maximum EU - (Multiplier * Maximum mV)
7.1 Example: A 4-20mA Water Level Sensor
In this example, we have a water level instrument connected to the iRIS Analogue Input 1. This instrument is designed to provide a nominal
1.Power up the installation and allow to stabilize.
2.Set the instrument to zero water level (using a calibrator)
3.Note the actual voltage measured by the iRIS (view this on the LCD on “System Status 3” screen. See Section 5.2.5. The LCD screen example below shows 993mV for a 0m input level.
4.Now increase the instrument input to full scale (10m) using the calibrator. Again, note the measured voltage relating to this input level. This time it is 4961mV for a 10m level input.
AI1: 993 mV
AI2: 0 mV
AI3: 0 mV
AI4: 0 mV
AI1: 4961 mV
AI2: 0 mV
AI3: 0 mV
AI4: 0 mV
5.Using the iLink Scaling Calculator, enter the minimum and maximum measured voltages and the levels they represent in the appropriate fields. Click the “Calculate” button to generate the correct multiplier and offset parameters to use in the sensor setup menu for Sensor 1 as shown.
Min mV
Min WL
Max mV
Max WL
*Sensor 1 Cfg (Now: 0.000)
0 Exit
Source [1: Analog 1]
2 [Water Lvl]
3 Mode | Avg] |
4[ 0.00252]
5Offset [
6Log Multiplier [1000]
7Log Rate [15min]
8Alarms
9Data
>
60 | iQuest (NZ) Ltd - PO Box 15169, Hamilton, New Zealand Tel: +64 7 |