SBAU470 June   2026

 

  1.   1
  2.   Description
  3.   Get Started
  4.   Features
  5.   Applications
  6.   6
  7. 1Evaluation Module Overview
    1. 1.1 Introduction
    2. 1.2 Kit Contents
    3. 1.3 Specification
    4. 1.4 Device Information
    5. 1.5 Getting Started With the ADS124S18EVM
  8. 2Hardware
    1. 2.1 Analog and Digital Power Supplies
    2. 2.2 Analog Input Connections
    3. 2.3 Digital Signal and Connection
    4. 2.4 Serial Interface
    5. 2.5 EEPROM
    6. 2.6 Connecting to an External Controller
  9. 3Software
    1. 3.1 Software Description
    2. 3.2 ADS124S18EVM Software Installation
    3. 3.3 Device Manager Check
  10. 4EVM Operation and Implementation Results
    1. 4.1 Evaluation Setup
    2. 4.2 ADC Capture Settings
    3. 4.3 Register Configurations
    4. 4.4 Time Domain Display
    5. 4.5 Spectral Analysis Display
    6. 4.6 Histogram Analysis Display
  11. 5Hardware Design Files
    1. 5.1 Schematics
    2. 5.2 PCB Layouts
    3. 5.3 Bill of Materials (BOM)
  12. 6Additional Information
    1. 6.1 Trademarks
  13. 7Related Documentation
    1. 7.1 Supplemental Content

2.2 Analog Input Connections

Each terminal block on the ADS124S18EVM has a function for connecting external sensors and power. RTD_A, RTD_B, and RTD_C on terminal block J4 are designed for connecting a 2-, 3-, or 4-wire RTD for temperature measurement. RTD_D is an external input as the positive input of the voltage reference for radiometric measurement in RTD design, the reference voltage is generated when a current flows through R13 resistor using the RTD_D pin on J4.

Terminal block J5 provides connections for thermocouples and bridge sensors. TC+/Bridge+ and TC-/Bridge- are inputs for a thermocouple or bridge-based sensor. Terminal block J5 provides AVDD output that can be used as an excitation voltage for an external bridge sensor.

Terminal block J7 provides connections for a thermistor. NTC+ and NTC- are inputs for connecting the thermistor. REFOUT provides an option to use the internal voltage reference output (1.25V or 2.5V) from the ADS124S18 to excite the thermistor.

Finally, terminal block J8 provides connections for an external voltage and current measurement. Use resistor R45 as a shunt resistor to measure an external current input. Replace resistors R40 and R43 to meet ADS124S18 input range requirement for an external voltage input.

Table 2-1 shows the details for the screw terminal blocks:

Table 2-1 ADS124S18EVM Terminal Block Description
Terminal Block Input Label Description
J4:1

RTD_A

 RTD connection point A
J4:2 RTD_B

RTD connection point B
J4:3 RTD_C RTD connection point C
J4:4 RTD_D RTD connection point D
J5:1

Exc+

 Positive excitation input
J5:2

Sense+/REFP0

Positive remote sensing input
J5:3

Bridge+/TC+

Positive bridge or thermocouple input
J5:4

Bridge-/TC-

 Negative bridge or thermocouple input
J7:5

Sense-/REFN0

 Negative remote sensing input
J7:6

Exc-

Negative excitation input
J7:1

REFOUT

 Output from ADS124S18 integrated VREF
J7:2

NTC+

 Positive thermistor input
J7:3

NTC-

Negative thermistor input
J8:1

REFOUT

 Output from ADS124S18 integrated VREF
J8:2

V_IN

Voltage input
J8:3

VCOM

Common-mode input
J8:4

I_IN

Current input
J8:5

GND

Analog ground
ADS124S18EVM-PDK DC313A: Analog Input (J4, J7, J5, J8) Figure 2-3 DC313A: Analog Input (J4, J7, J5, J8).

Table 2-2 summarizes the required IDAC, and analog input channel settings to measure each RTD configuration with the ADS124S18EVM.

Table 2-2 ADS124S18EVM Settings for Different RTD Types
RTD No. of IDACs RREF Resistor IDAC Channels AINP AINN
2-Wire 1 Low-Side AIN15 AIN1 AIN0
3-Wire 1 Low-Side AIN15 AIN1(1) AIN2(1)
AIN2(2) AIN0(2)
2 Low-Side AIN15, AIN3 AIN1 AIN2
4-Wire 1 Low-Side AIN15 AIN2 AIN4
(1) First measurement.
(2) Second measurement.

Figure 2-4 and Figure 2-5 show the configuration diagrams for 2-, 3-, 4-wire RTD measurements supported by the ADS124S18EVM.

ADS124S18EVM-PDK ADS124S18EVM: 3-wire RTD Measurement With One and Two IDACs Figure 2-4 ADS124S18EVM: 3-wire RTD Measurement With One and Two IDACs
ADS124S18EVM-PDK ADS124S18EVM: 2-, 4-Wire RTD Measurement With One IDAC Figure 2-5 ADS124S18EVM: 2-, 4-Wire RTD Measurement With One IDAC

Figure 2-6 shows a circuit to bias the thermocouple sensor that the ADS124S18EVM supports. The circuit uses a thermistor for cold-junction compensation (CJC). The red arrows indicate external jumper wires that must be provided by the user. Refer to the application note for more information on thermocouple measurement: A Basic Guide to Thermocouple Measurements.

ADS124S18EVM-PDK ADS124S18EVM: Thermocouple Measurement With a Thermistor for CJC Figure 2-6 ADS124S18EVM: Thermocouple Measurement With a Thermistor for CJC

Figure 2-7 shows a circuit for a bridge measurement that the ADS124S18EVM supports. The circuit uses a thermistor for temperature compensation of the bridge. The red arrows indicate external jumper wires that must be provided by the user. Refer to the application note for more information on thermocouple measurement: A Basic Guide to Bridge Measurements.

ADS124S18EVM-PDK ADS124S18EVM: Resistive Bridge Measurement With a Thermistor for Compensation Figure 2-7 ADS124S18EVM: Resistive Bridge Measurement With a Thermistor for Compensation