How to Use ANALOG INPUTS TO RS-485 : Examples, Pinouts, and Specs

The ADAM-4117, manufactured by NI National Instrument, is a versatile analog-to-digital signal conversion module. It is designed to convert analog signals into a digital format suitable for transmission over RS-485 communication lines. This component is widely used in industrial environments for long-distance data acquisition and monitoring.

• Industrial automation and process control
• Remote data acquisition systems
• Environmental monitoring
• Factory equipment monitoring
• SCADA (Supervisory Control and Data Acquisition) systems

The ADAM-4117 is particularly valued for its ability to handle multiple analog input channels and transmit data reliably over long distances using the RS-485 protocol.

• Manufacturer: NI National Instrument
• Part ID: ADAM-4117
• Input Channels: 8 differential analog input channels
• Input Range: ±10V, ±5V, ±1V, ±500mV (software configurable)
• Resolution: 16-bit
• Communication Protocol: RS-485
• Baud Rate: 1,200 to 115,200 bps
• Power Supply: 10 to 30 VDC
• Isolation Voltage: 3,000 VDC
• Operating Temperature: -10°C to 70°C
• Accuracy: ±0.1% of full scale

The ADAM-4117 module features a terminal block for wiring connections. Below is the pin configuration:

1. Power Supply: Connect a DC power supply (10-30 VDC) to the +V and GND pins.
2. Analog Inputs: Wire the analog sensors or devices to the appropriate AI+ and AI- pins for each channel.
3. RS-485 Communication: Connect the DATA+ and DATA- pins to the RS-485 network.
4. Configuration: Use the provided software or commands to configure the input range, baud rate, and other parameters.
5. Data Acquisition: Once configured, the module will continuously convert analog signals to digital data and transmit it over the RS-485 network.

• Ensure proper grounding to avoid noise interference in analog signals.
• Use shielded cables for analog inputs to minimize electromagnetic interference (EMI).
• Match the baud rate and communication settings of the ADAM-4117 with the RS-485 master device.
• Terminate the RS-485 network with a 120-ohm resistor at both ends to prevent signal reflections.
• Avoid exceeding the input voltage range to prevent damage to the module.

The ADAM-4117 can be interfaced with an Arduino UNO using an RS-485 module. Below is an example code snippet:

#include <SoftwareSerial.h>

// Define RS-485 communication pins
#define RS485_RX 10  // Arduino pin connected to RS-485 module RX
#define RS485_TX 11  // Arduino pin connected to RS-485 module TX

// Create a SoftwareSerial object for RS-485 communication
SoftwareSerial rs485(RS485_RX, RS485_TX);

void setup() {
  // Initialize serial communication
  Serial.begin(9600);  // For debugging via Serial Monitor
  rs485.begin(9600);   // RS-485 communication baud rate

  // Send initialization command to ADAM-4117
  rs485.print("#01\r");  // Example command to read data from channel 1
  delay(100);
}

void loop() {
  // Check if data is available from ADAM-4117
  if (rs485.available()) {
    String data = "";
    while (rs485.available()) {
      char c = rs485.read();
      data += c;
    }
    // Print received data to Serial Monitor
    Serial.println("Received Data: " + data);
  }
}

Note: Replace #01\r with the appropriate command for your application. Refer to the ADAM-4117 command set for details.

1. No Data Received

   • Cause: Incorrect baud rate or communication settings.
   • Solution: Verify and match the baud rate and settings between the ADAM-4117 and the RS-485 master device.

2. Analog Input Readings Are Incorrect

   • Cause: Input voltage exceeds the configured range or improper wiring.
   • Solution: Check the input voltage range and ensure proper wiring of the analog inputs.

3. RS-485 Communication Fails

   • Cause: Missing termination resistors or incorrect wiring.
   • Solution: Add 120-ohm termination resistors at both ends of the RS-485 network and verify wiring.

4. Module Overheating

   • Cause: Power supply voltage exceeds the specified range.
   • Solution: Ensure the power supply voltage is within 10-30 VDC.

• Q: Can the ADAM-4117 handle single-ended inputs?
  A: No, the ADAM-4117 is designed for differential input signals only.

• Q: What is the maximum cable length for RS-485 communication?
  A: RS-485 supports cable lengths up to 1,200 meters (4,000 feet) at lower baud rates.

• Q: How many ADAM-4117 modules can be connected on the same RS-485 network?
  A: Up to 32 devices can be connected on a single RS-485 network without repeaters.

• Q: Is the module compatible with Modbus protocol?
  A: Yes, the ADAM-4117 supports Modbus/RTU communication.

By following this documentation, users can effectively integrate the ADAM-4117 into their industrial systems for reliable and accurate data acquisition.