Terminal 2

Terminal 2 provides isolated digital inputs and isolated analog inputs for voltage and current measurement.

Isolated Digital Input

Specifications

Parameter	Minimum	Maximum	Unit
Low Level (VIL)	-50	0.8	V
High Level (VIH)	3	50	V
Minimum ON Current	0.2	-	mA
Isolation Voltage	-	3750	Vrms

Characteristics

Input type: Wet contact (requires external voltage source) Control logic: Active HIGH Number of channels: 4 (DI0, DI1, DI2, DI3) Isolation: Each channel isolated from system and from other channels

GPIO Mapping

Input	GPIO Pin
DI0	GPIO13
DI1	GPIO17
DI2	GPIO22
DI3	GPIO27

Wiring

Each digital input requires an external voltage source (wet contact configuration):

• Positive terminal (+): Connect to signal source
• Negative terminal (-): Connect to signal ground

Minimum activation: DC 3.0V at 0.2mA Maximum input: DC 50V

Example - Connecting a 24V sensor:

Sensor Output (+) ----[DI0 +]
Sensor Ground     ----[DI0 -]

When sensor outputs 3V or higher, GPIO13 reads HIGH.

Important Notes

• Inputs are wet contact only - they require external power
• Dry contact signals (unpowered switches) will not work
• Each channel is isolated from the others and from system ground

Isolated Analog Input

Specifications

Parameter	Minimum	Maximum	Unit
Voltage Mode Range	0	10	V
Voltage Mode (0-5V)	0	5	V
Current Mode Range	0	20	mA
Input Impedance (Voltage)	-	25	kΩ
Input Impedance (Current)	-	250	Ω
Isolation Voltage	-	3000	Vrms

ADC Specifications

Chip: ADS1115 Interface: I2C Slave Address 0x48 Channels: 4 (AI0, AI1, AI2, AI3) Resolution: 16-bit Full Scale Range: Configurable via gain setting

Operating Modes

The analog inputs support three measurement modes:

• 0-5V voltage measurement
• 0-10V voltage measurement
• 0-20mA current measurement

Important: All four channels share the same mode, configured via internal DIP switch.

Voltage Mode Configuration

For 0-5V or 0-10V measurements:

1. Set internal Analog Input Mode Switch to voltage position
2. Connect signal to AI[n] + terminal
3. Connect ground to AGND terminal

Input impedance: 25kΩ

Current Mode Configuration

For 0-20mA measurements:

1. Set internal Analog Input Mode Switch to current position
2. DIP switch MUST be ON to enable internal shunt resistor
3. Connect current loop to AI[n] + terminal
4. Connect current return to AGND terminal

Input impedance: 250Ω (shunt resistor)

AGND Isolation

⚠️ Important: AGND is isolated from system ground but common among all four analog input channels.

• Do not connect AGND to system ground
• All four analog inputs share the same AGND reference
• AGND isolation: 3000 Vrms from system ground

Wiring Examples

Voltage measurement (0-10V sensor):

Sensor Output (+) ----[AI0]
Sensor Ground     ----[AGND]

Current measurement (0-20mA sensor):

Sensor Current Output (+) ----[AI0]
Sensor Current Return     ----[AGND]

Ensure DIP switch is set to current mode and enabled.

ADC Python Library

Recommended library: Adafruit_ADS1x15

Installation:

pip install Adafruit_ADS1x15

Initialization:

import Adafruit_ADS1x15

# Initialize ADC
adc = Adafruit_ADS1x15.ADS1115(address=0x48, busnum=1)

Reading voltage (0-10V):

# Read ADC (channel 0, gain 1 for 0-10V)
val = adc.read_adc(0, gain=1)

# Calculate voltage
# Full scale: 32767 @ 4.096V * 2.5 (divider) = 10.24V
voltage = val / 3200  # Result in volts

Reading voltage (0-5V):

# Read ADC (channel 0, gain 2 for 0-5V)
val = adc.read_adc(0, gain=2)

# Calculate voltage
# Full scale: 32767 @ 2.048V * 2.5 (divider) = 5.12V
voltage = val / 6400  # Result in volts

Reading current (0-20mA):

# Read ADC (channel 0, gain 2 for 0-20mA)
# DIP switch must be ON to enable shunt resistor
val = adc.read_adc(0, gain=2)

# Calculate current
# Full scale: 32767 @ 2.048V * 2.5 (divider) / 250Ω = 20.48mA
current = val / 1600  # Result in mA

Calculation Details

0-10V mode (gain=1):

• ADC full scale: 32767 = 4.096V
• Voltage divider: 2.5×
• Maximum measurable: 4.096V × 2.5 = 10.24V
• Conversion: voltage = val / 3200

0-5V mode (gain=2):

• ADC full scale: 32767 = 2.048V
• Voltage divider: 2.5×
• Maximum measurable: 2.048V × 2.5 = 5.12V
• Conversion: voltage = val / 6400

0-20mA mode (gain=2):

• ADC full scale: 32767 = 2.048V
• Voltage divider: 2.5×
• Shunt resistor: 250Ω
• Maximum measurable: (2.048V × 2.5) / 250Ω = 20.48mA
• Conversion: current = val / 1600

Common Issues

Digital Input Issues

• No response from dry contact switch - Digital inputs require wet contact (external voltage)
• Voltage below 3.0V - Input will not register as HIGH
• Voltage above 50V - May damage input circuitry

Analog Input Issues

• Current mode not working - DIP switch must be enabled for shunt resistor
• All channels must use same mode - Cannot mix voltage and current on different channels
• AGND connected to system ground - AGND is isolated; do not connect to system ground
• Wrong ADC gain setting - Use gain=1 for 0-10V, gain=2 for 0-5V and 0-20mA

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Source(s):

• IRIV PiControl CM4 User Manual, Rev 1.3, Nov 2025, Sections 2, 4, 5.2