Optiquest iRIS 220 manual Internal / External 12V Battery Supply, External Charger Power Supply

15 - iRIS 220 / iRIS 320, V1.19 User Guide

3.4.2 Internal / External 12V Battery Supply

For all models there are two terminals provided on the I/O connector designated +12V and GND (or –12V on old models). These can be used to power the unit from an external 12V battery or regulated dc supply. For the iRIS 320 / iRIS 320V models, the internal battery is effectively connected directly to these terminals. See Section 3.4.1 for warnings on connecting external power supplies to them.

3.4.3 External (Charger) Power Supply

Although the iRIS 320 can operate solely from its internal battery for a few days, you will typically need to connect an external supply to the unit so that the internal battery remains in a charged state. You can connect any external dc power source ranging from 15 – 30Vdc, including a solar panel, without requiring an additional solar regulator.

The battery charging circuitry utilises a switch mode regulator for maximum efficiency. The external power supply is protected against over-voltage by ultra-fast acting protection devices and a self-resetting semiconductor fuse.

It can also be used to charge an external battery connected to the GND and 12V+ terminals. In the event that the external battery draws excessive current, the charger will enter a current limit mode (900mA) until such time as the battery has been recharged sufficiently to deliver the full supply voltage. The charging profile used by the charger depends on the selected mode. See the Power Management description in Section 4.3.1.

3.4.4 Analog Inputs

The four analogue inputs are uni-polar 0-5Vdc with 12-bit resolution. Each input presents a load impedance of 98KΩ to the input signal.

Scaling factors should be chosen to convert from a raw value of 0-5000, which reflects the input signal range of 0-5V (0-5000mV). When current sources such as 0-20mA or 4-20mA are used, an external sink resistor (typically 250Ω) must be fitted between the analogue input and AGND.

NOTE: As the analogue inputs have an input impedance of 98KΩ, the actual sink impedance will be slightly lower than the value fitted. For example, a sink resistor of 250 ohms is installed. The actual impedance will theoretically be 249.36Ω; therefore the voltage measured by the iRIS will also be slightly lower than expected.

AINx

51K

47K

To ADC

100nF

AGND

Figure 5 - Analog Input Circuit