Function Modules 8 Configurable Channels of Either RTD Measurement or Thermocouple

The TR1 provides 8 channels which can be individually programmed as a Thermocouple (TC) or a Resistance Temperature Detector (RTD) measurement interface. When configured as a TC, the channel can interface with virtually all thermocouple-type NIST temperature ranges. When configured as an RTD, the channel can interface to two, three and four-wire platinum RTD sensor configurations. The TR1 channels are individually configurable for up to 8 isolated TC or low-voltage range A/D measurement channels. Configuration programmability provides interfaces for industry standard NIST thermocouple types (J, K, T, E, N, B, R, and S). The TR1 channels are individually configurable for up to 8 isolated RTD measurement channels. Each channel is configurable for use with 4-wire, 3- wire or 2-wire connections to the RTD sensors. All RTD channels provide measurement results in Single Precision Floating Point Value (IEEE-754) format.

Interfaces with most standard NIST thermocouple types (J, K, T, E, N, B, R, and S) Self-powered Large temperature range; up to 2300° C Accuracy up to ±0.2° C (thermocouple type dependent)

Thermo-block compensation option P/N ACC-ISO-THERM-BLK2 (If accessory used, channel 8 is automatically allocated as an RTD interface for the thermo-block compensation temperature measurement)

Higher accuracy and repeatability as compared with thermocouples in applications below 600 °C

Two, three or four-wire mode

Single Precision Floating Point Value (IEEE-754) format

Open sensor connections are detected and reported

1 mA, 500 µA, 250 µA & 100 µA excitation sources for Pt100, Pt500, Pt1000 and Pt2000 ranges

Up to 8 RTD channels

Up to 8 Thermocouple channels

Configures Thermocouple or RTD

Sets the sampling rate of the A/D

Provides ability to null for any system induced measurement errors

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NAI’s Custom-On-Standard Architecture™ (COSA®) offers a choice of over 40 Intelligent I/O, communications, or Ethernet switch functions, providing the highest packaging density and greatest flexibility of any 3U SBC in the industry. Preexisting, fully-tested functions can be combined in an unlimited number of ways quickly and easily.

The 75PPC1 includes BSP and SDK support for Wind River® VxWorks®. In addition, software support kits are supplied, with source code and board-specific library I/O APIs, to facilitate system integration. Each I/O function has dedicated processing, unburdening the SBC from unnecessary data management overhead.

BIT continuously monitors the status of all I/O during normal operations and is totally transparent to the user. SBC resources are not consumed while executing BIT routines. This simplifies maintenance, assures operational readiness, reduces life-cycle costs and— keeps your systems mission ready.

Eliminate man-months of integration with a configured, field-proven system from NAI. Specification to deployment is a seamless experience as all design, state-of-the-art manufacturing, assembly and test are performed— by one trusted source. All facilities are in the U.S. and optimized for high-mix/low volume production runs and extended lifecycle support.

From design-in to production, and beyond, NAI’s product lifecycle management strategy ensures the long-term availability of COTS products through configuration management, technology refresh, and obsolescence component purchase and storage.

As a leading manufacturer of smart function modules, NAI offers over 100 different modules that cover a wide range of I/O, measurement and simulation, communications, Ethernet switch, and SBC functions. Our TR1 smart function module provides 8 channels which can be individually configured as a Thermocouple (TC) or Resistance Temperature Detector (RTD) measurement interface. This user manual is designed to help you get the most out of our Thermocouple/RTD smart function module.

NAI’s TR1 module offers a range of advanced features tailored to meet the demands of precision measurement applications, both in Thermocouple mode and RTD mode, including the following:

NIST Thermocouple Interface Capability:

In thermocouple mode, the TR1 module features configuration programmability which provides interfaces for all standard NIST thermocouple types (J, K, T, E, N, B, R, and S), providing unparalleled versatility in thermocouple compatibility.

Self-Powered:

One standout feature of the thermocouple mode is its self-powered functionality, eliminating the need for external power sources and simplifying installation. This not only streamlines the setup process but also enhances its suitability for a wide range of applications.

Large Temperature Range:

The thermocouple function boasts an expansive temperature measurement range, reaching a remarkable 2300⁰C. This exceptional range makes it well-suited for applications where extreme temperatures are encountered, such as jet engines and gas turbine exhaust. Up to ±0.2⁰C Accuracy: With thermo-block compensation, the thermocouple provides compensated measurements at accuracies up to ±0.2⁰C.

Optional Thermo-Block Compensation:

NAI offers an optional accessory (ACC-ISO-THERM-BLK2) which connects to the thermocouple sensors, allowing for automatic cold junction compensation temperature through an onboard RTD temperature sensor (CH8 will automatically configure to RTD mode if this accessory is used).

Higher Accuracy and Repeatability:

The TR1’s RTD mode excels in accuracy and repeatability when compared to thermocouples, making it an ideal choice for applications with operating temperatures below 600°C. This characteristic ensures that critical measurements are obtained with the utmost precision.

Wire Modes:

The module provides flexibility with two, three, or four-wire modes, allowing users to adapt to various measurement setups and requirements, enhancing versatility in different scenarios.

Data Format:

The TR1 module utilizes the Single Precision Floating Point Value (IEEE-754) format for data representation, enabling compatibility and ease of integration with other systems and equipment. Open Sensor Detection: When configured for RTD mode, the TR1 module is equipped with a built-in feature to detect and report open sensor connections. This safeguards against inaccurate measurements caused by sensor failures, promoting data integrity.

Excitation Sources:

To accommodate various RTD ranges when configured for RTD mode, the TR1 provides excitation sources of 1 mA (Pt100), 500 μA (Pt500), 250 μA (Pt1000), and 100 μA (Pt2000) for 2- & 4-wire modes, and 500 μA (Pt100), 250 μA (Pt500), 125 μA (Pt1000), and 50 μA (Pt2000) for 3-wire mode. This feature ensures precise measurements across a wide range of applications.

Independently Programmable:

The TR1 module offers the capability to independently program up to 8 RTD or Thermocouple channels. This feature is invaluable for engineers working on complex systems with multiple measurement points, allowing for tailored configuration and control.

Programmable Sample Rate:

Users can set the sampling rate of the analog-to-digital converter (A/D) to match the specific needs of their application. This programmable sample rate ensures that data acquisition is optimized for accuracy and efficiency.

Offset Temperature:

The offset temperature feature provides users with the means to nullify system-induced measurement errors. This is crucial in achieving the highest level of measurement precision and reliability, especially in critical applications where accuracy is paramount.

The TR1 is programmable for either Thermocouple or RTD measurement via the Mode Select register.

While in thermocouple mode, the TR1 provides up to eight individual isolated thermocouple or low-voltage range A/D measurement channels. Configuration programmability provides interfaces for industry standard NIST thermocouple types (J, K, T, E, N, B, R, and S).

Thermocouples are widely used temperature-measurement devices because of their ruggedness, repeatability and fast response time. They offer a cost-effective means for measuring a much wider range of temperatures in comparison to other common solutions like resistance temperature devices (RTD), thermistors, or temperature-sensing integrated circuits (ICs). Although thermocouples can be used over a wider range of temperatures than RTDs and temperature-sensing ICs, they are far less linear. Also, RTDs and temperature-sensing ICs typically offer better sensitivity and accuracy. Thermocouple signals are very low-level and often require amplification or a high-resolution data converter to process the signals. Despite these disadvantages, overall cost, ease of use, and wide temperature range make thermocouples popular.

Thermocouples are constructed with two wires made from dissimilar metals. One wire is predesignated as the positive side, and the other as the negative. The industry standard NIST thermocouple types are defined by the metals or alloys used and the temperature range allowed for each type. Each thermocouple type offers a unique thermoelectric characteristic over its specified temperature range.

In Figure 1, the voltage generated by the loop is a function of the temperature difference between the two junctions. This phenomenon is known as the Seebeck effect which is described as the process in which thermal energy is converted into electrical energy. The Peltier effect is the opposite of the Seebeck effect which is the process of converting electrical energy to thermal energy. In Figure 1, the measure output voltage (V ) is a function of the difference between the measuring (hot) junction voltage and the reference (cold) junction voltage. Since V and V are generated by a temperature difference between the two junctions, V is also a function of this temperature difference. The scale factor, α (Seebeck coefficient), relates the voltage difference to the temperature difference.

Figure 2 illustrates the configuration most commonly used in thermocouple applications. In this configuration, a third metal (known as an intermediate metal) such as copper, is introduced into the loop and the two additional junctions. In this configuration, provided the two junctions are at the same temperature, the intermediate metal type has no effect on the output voltage. This configuration allows the thermocouple to be used without a separate reference junction. V is still a function of the difference between the hot- and cold-junction temperature, related by the Seebeck coefficient. In this configuration, the cold-junction temperature must be known in order to determine the actual temperature measured at the hot-junction.

The simplest case occurs when the cold-junction temperature is at 0° C, also known as an ice-bath reference. At T = 0° C, V = V . In this case, the voltage measured at the hot-junction is a direct translation of the actual temperature at that junction.

When the cold-junction temperature is not at 0° C, the temperature of this junction must be known in order to determine the actual hot-junction temperature. The output voltage of the thermocouple must also be compensated to account for the voltage created by the nonzero cold-junction temperature. This process is known as cold-junction compensation.

NAI provides an optional accessory, NAI P/N ACC-ISO-THERM-BLK2, a thermocouple connection interface comprised of a separate isothermal interface/terminal block. The thermocouple sensors are connected to the accessory’s copper measurement wiring harness, allowing for automatic cold junction compensation temperature through an onboard RTD temperature sensor reporting the terminal temperature to a dedicated channel on the module (refer to Appendix A: Optional External Cold Junction Compensation Block Accessory).

In lieu of the External Cold Junction Compensation Block Accessory, a user supplied terminal connection block may also be used, provided the terminal temperature is measured and maintained in the manual cold junction compensation temperature register for proper compensation. A benefit of this would be the availability of Channel 8 for an additional Thermocouple or RTD measurement channel.

In addition to cold-junction temperature compensation, the TR1 provides the ability to program temperature offsets, which can be used to null out small temperature deviations from sensors or system interconnections as well as delta measurements from an initial temperature reading. The offset temperature is subtracted from the output temperature reading and may be configured individually for each channel.

The fundamental design of the TR1 is based on independent 24-bit Sigma-Delta A/D converters for each channel. This allows the TR1 to also be used for direct precision low voltage measurements (±78.125 mV) for uses in low-voltage range A/D applications (i.e. shunt resistor voltage/current sense measurements).

TR1 is designed for rugged embedded “on-the-move” or laboratory-grade environments, and provides continuous background built-in-test (BIT) capabilities for accuracy and “open” detection monitoring and flagging.

The TR1 channels are individually configurable for up to 8 RTD measurement channels. Each channel is configurable for use with 4-wire, 3-wire or 2-wire connections to the RTD sensors. All RTD channels are calibrated at the factory and measurement results provided in Single Precision Floating Point Value (IEEE-754) format.

Open sensor connections are detected and reported in an Open status word. A 1mA excitation source is used for resistance measurement in the lowest range setting (Pt100). For the Pt500, Pt1000 and Pt2000 ranges, the excitation current sources are 500µA, 250µA, and 100µA respectively.

Lead resistance correction is available in 2-wire mode, allowing for user compensation of cabling resistance in the measurement system. Resistance values may be entered for individual channels, which are subtracted from the measurement. The temperature measurements will reflect the compensated resistance values for the RTD for direct readout of the corrected temperature readings.

As with the Thermocouple mode, the temperature offset provisions allow for the same nulling of the temperature offsets in the system and operate similarly.

2-Wire is the simplest resistance measurement configuration, requiring only two wires per sensor. Measurements will be very sensitive to test cabling, as the excitation current and voltage measurements are through the same wires. Short or low resistance test leads are needed for accurate readings. Provisions for nulling the test lead resistances are provided via individual 2-wire offset resistance registers, allowing direct readings of the compensated measurements on a per channel basis.

3-Wire configuration relies on balanced test lead resistance on the Sense (+) and Sense (-) wires, so the voltage drop across each of the two current source lines are equal and cancel each other out. The differential voltage reading between the two sense lines along with the excitation current through the resistor is used in the resulting calculation of the sensor resistance. The test lead wire length will not affect the measurement provided the two lines are equal in resistance and is often the best compromise between wiring requirements and accuracy. In 3-Wire mode, the excitation current is split in half. Half of the total current flows on each of the sense lines (see 3-Wire RTD connection diagram).

4-Wire configuration provides optimal accuracy, allowing precise measurements without any constraints of short or balanced test leads, but requires 4 wires per sensor. The two sense wires measure the voltage at the sensor independently without undue influence of voltage drops due to the excitation current. This configuration is recommended where accuracy is a priority over the additional wiring requirements.

The module can measure low voltage dynamic signals in the microvolt range with faster update rates to 4800 Hz. Readings can track dynamic signals when high rates are selected, with some increase in noise jitter. Optimal accuracy and reading stability will be achieved by low update rate selections.

Default configuration runs periodic maintenance in the background for self-test and calibration at 30 second intervals, which briefly suspends reading updates during the performance of these routines. For time critical measurements, the periodic internal processes may optionally be suspended for continuous and uninterrupted readings. During this time, these maintenance operations may be triggered manually by the user at suitable intervals.

Automatic background BIT testing is provided. Each channel is checked at periodic intervals for correct A/D operation using an internal measurement of an on-board resistor reference. The open input detection test applies a low-level current pulse to the A/D converter inputs and tests for a full-scale 3.3V limit, indicating an open sensor circuit. Any failure triggers an interrupt if enabled, with the results available in the status registers. The testing is transparent to the user and has no effect on the operation of this module. Enabled by default at power on, it may optionally be disabled.

The TR1 provides the ability to program two temperature thresholds that will result in temperature alerts. For each threshold, a “low” and a “high” threshold value is specified that will be used to set the Temperature Alert statuses. The Temperature Threshold Low registers sets the threshold values to use to set the Temperature Alert Low status bit when the Temperature reading is below the low temperature threshold value. Conversely, the Temperature Threshold High registers sets the threshold values to use to set the Temperature Alert High status bit when the Temperature reading is above the high temperature threshold value. These threshold values are individually configurable on a per channel basis. A possible usage of the two temperature thresholds is to use the first threshold detection levels as an early warning pre-alarm level and the second threshold detection levels as an alarm limit value. For this purpose, the Detect 2 thresholds should be set at larger deviation values from the nominal temperature than the Detect 1 thresholds.

For example:

[Threshold Low 2] < [Threshold Low 1] < [Nominal Temperature] < [Threshold High 1] < [Threshold High 2]. This allows the Detect 1 thresholds to serve as a pre-alert warning of temperature excursion, while Detect 2 may represent an alarm condition.

The TR1 Function Module provide registers that indicate faults or events. Refer to “Status and Interrupts Module Manual” for the Principle of Operation description.

The TR1 Function Module includes module common registers that provide access to module-level bare metal/FPGA revisions & compile times, unique serial number information, and temperature/voltage/current monitoring. Refer to “Module Common Registers Module Manual” for the detailed information.

The register descriptions provide the Register Name, Type, Data Range, Read or Write information, power on default initialized values, a description of the function and a data table where applicable,

The TR1 measurement registers provide Temperature measurements (in both Celsius and Fahrenheit degrees), for RTD mode, Resistance measurements, and for Thermocouple mode, Voltage measurements.

When the TR1 module channel is configured for Thermocouple mode, in addition to the temperature measurements, the Voltage measurement is also available.

When the TR1 module channel is configured for RTD mode, in addition to the temperature measurements, the Resistance measurement is also available.

The TR1 control registers provide the ability to configure the channels to either Thermocouple or RTD mode and specifying the sample rate. For Thermocouple channels, the configuration requirements include specification of the Thermocouple type and Thermocouple temperature compensation settings. For RTD channels, configuration requirements include specifying the RTD type, the RTD wire-measurement mode and resistance compensation (resistance compensation is only required for channels configured in 2-Wire mode).

For TR1 module channels configured in Thermocouple mode, additional configurations and controls include the Thermocouple Type, Automatic Cold Junction Compensation Enable, the Compensation Type, and the Compensation Temperature.

For time critical measurements, such as using a channel for low voltage A/D measurements, the TR1 module provides registers to suspend the maintenance operations which briefly suspends the updates of measurement readings.

The default configuration of the module is to run periodic self-test and calibration at 30 second intervals. During these operations, updates to the measurement readings are briefly suspended. For time critical measurements, such as using a channel for low voltage A/D measurements, the periodic internal processes may optionally be suspended for continuous and uninterrupted readings. During this suspended time, the maintenance operations for calibration and open-line detect may be triggered manually by the application at suitable intervals.

For TR1 module channels configured in RTD mode, additional configurations and controls include the RTD Type, Wire Measurement Mode and 2- Wire Lead Resistance Compensation

The TR1 Temperature Threshold registers provide the ability program two temperature thresholds that will result in temperature alerts.

A “low” and a “high” threshold value is specified for each temperature threshold that will be used to set the Temperature Alert statuses. The Temperature Threshold Low 1 register sets the threshold value to use to set the Temperature Alert Low 1 status bit when the Temperature reading is below the low temperature threshold value. Conversely, the Temperature Threshold High 1 register sets the threshold values to use to set the Temperature Alert High 1 status bit when the Temperature reading is above the high temperature threshold value. These threshold values are individually configurable on a per channel basis.

A “low” and a “high” threshold value is specified for each temperature threshold that will be used to set the Temperature Alert statuses. The Temperature Threshold Low 2 register sets the threshold value to use to set the Temperature Alert Low 2 status bit when the Temperature reading is below the low temperature threshold value. Conversely, the Temperature Threshold High 2 register sets the threshold values to use to set the Temperature Alert High 2 status bit when the Temperature reading is above the high temperature threshold value. These threshold values are individually configurable on a per channel basis.

Key: Bold Italic = Configuration/Control

Bold Underline = Measurement/Status

*When an event is detected, the bit associated with the event is set in this register and will remain set until the user clears the event bit. Clearing the bit requires writing a 1 back to the specific bit that was set when read (i.e. write-1-to-clear, writing a ‘1' to a bit set to ‘1' will set the bit to ‘0'). ~ Data is always in Floating Point.

Refer to “Module Common Registers Module Manual” for the Module Common Registers Function Register Map.

BIT Status

Open

Temperature Alert Low 1

Temperature Alert Low 2

Temperature Alert High 1

Temperature Alert High 2

Summary Status

The Interrupt Vector and Interrupt Steering registers are located on the Motherboard Memory Space and do not require any Module Address Offsets. These registers are accessed using the absolute addresses listed in the table below.

Thermocouple applications require an interface from the base motherboard/module to the thermocouple wires, providing a transition from the thermocouple wires to conventional (copper) wiring for the measurement. Conventional wiring (copper), when connected to the thermocouple wire, will create a junction of dissimilar metals. When a junction of dissimilar metals occurs at temperatures other than a standard 0.0 deg C, there will be an additional voltage gradient developed, acting as an additional thermocouple and affecting the reading of the primary thermocouple. Compensation is required for this temperature delta offset. The effect of the junction temperature needs to be factored into the measurement to provide the correct readings. The effects of the temperature reading on the measurement is not a direct arithmetic correction due to the nonlinear response characteristics of thermocouples. The compensation calculations involve the thermocouple type and the temperature measurement points.

The primary purpose of the isothermal block is to provide a consistent temperature environment for the terminal blocks connecting thermocouple wires to the system interface to the motherboard/module and provides the measurement of the junction temperature. This allows the cold junction compensation temperature to be done automatically. The isothermal block contains an RTD temperature sensor and is constructed to minimize temperature variances between channels and the isothermal block itself. The sensor is read by a designated RTD channel (Ch.8) to allow automatic compensation with the junction temperature measurement.

The NAI P/N ACC-ISO-THERM-BLK2 is a semi-rugged, non-sealed housing designed with terminals to secure up to 7 thermocouple interconnects (one for each available channel of the TR1). It is designed to be mounted/secured to a “cold plate” (surface/mass that is expected to maintain a relatively stable and constant temperature over time). The isothermal block has an embedded Pt100 RTD temperature sensor for measurement of the junction temperature. The TR1 module, when programmed for external block compensation mode, will utilize this reference temperature reading and provide automatic thermocouple measurement compensation based on the temperature reading of the sensor.

Tolerance contribution from measurement tolerances of +/-25µV, independent of tolerance contributions of cold junction compensation and individual TC sensors.

Pin-out details (for reference) are shown below, with respect to DATAIO. Additional information on pin-outs can be found in the Motherboard Operational Manuals.

TR1 HARDWARE BLOCK DIAGRAM

TR1 PROCESSING BLOCK DIAGRAM

This section identifies the firmware revision in which specific features were released. Prior revisions of the firmware would not support the features listed.

Status registers indicate the detection of faults or events. The status registers can be channel bit-mapped or event bit-mapped. An example of a channel bit-mapped register is the BIT status register, and an example of an event bit-mapped register is the FIFO status register.

For those status registers that allow interrupts to be generated upon the detection of the fault or the event, there are four registers associated with each status: Dynamic, Latched, Interrupt Enabled, and Set Edge/Level Interrupt.

Dynamic Status: The Dynamic Status register indicates the current condition of the fault or the event. If the fault or the event is momentary, the contents in this register will be clear when the fault or the event goes away. The Dynamic Status register can be polled, however, if the fault or the event is sporadic, it is possible for the indication of the fault or the event to be missed.

Latched Status: The Latched Status register indicates whether the fault or the event has occurred and keeps the state until it is cleared by the user. Reading the Latched Status register is a better alternative to polling the Dynamic Status register because the contents of this register will not clear until the user commands to clear the specific bit(s) associated with the fault or the event in the Latched Status register. Once the status register has been read, the act of writing a 1 back to the applicable status register to any specific bit (channel/event) location will “clear” the bit (set the bit to 0). When clearing the channel/event bits, it is strongly recommended to write back the same bit pattern as read from the Latched Status register. For example, if the channel bit-mapped Latched Status register contains the value 0x0000 0005, which indicates fault/event detection on channel 1 and 3, write the value 0x0000 0005 to the Latched Status register to clear the fault/event status for channel 1 and 3. Writing a “1” to other channels that are not set (example 0x0000 000F) may result in incorrectly “clearing” incoming faults/events for those channels (example, channel 2 and 4).

Interrupt Enable: If interrupts are preferred upon the detection of a fault or an event, enable the specific channel/event interrupt in the Interrupt Enable register. The bits in Interrupt Enable register map to the same bits in the Latched Status register. When a fault or event occurs, an interrupt will be fired. Subsequent interrupts will not trigger until the application acknowledges the fired interrupt by clearing the associated channel/event bit in the Latched Status register. If the interruptible condition is still persistent after clearing the bit, this may retrigger the interrupt depending on the Edge/Level setting.

Set Edge/Level Interrupt: When interrupts are enabled, the condition on retriggering the interrupt after the Latch Register is “cleared” can be specified as “edge” triggered or “level” triggered. Note, the Edge/Level Trigger also affects how the Latched Register value is adjusted after it is “cleared” (see below).

The registers described in this document are common to all NAI Generation 5 modules.