The standard defines a collection of templates for common classes of transducers as listed in Table 2. Templates 25 through 39 are transducer type templates that contain properties that are needed for the specific types of transducers. Templates 40, 41, and 42 are calibration templates and can be used with one of the transducer type templates.
The tables in the following sections summarize the contents of each IEEE standard template. Each row of the table corresponds to a property command (designated in templates with the % sign) or control command that utilizes bits from the TEDS, such as a Select Case. The first column in many of the tables, labeled Select, indicate the different cases for Select Cases in the templates. For example, a 2 bit Select Case read from the TEDS may have four different cases, each containing a section of template that is used for the corresponding Select Case value.
The tables also detail the number of bits used for each property, the access level (user, calibration, or identification), and the data type. The datatypes used in these standard templates are summarized in Table 3.
Table 3. Data Types Used in IEEE Standard Templates
|ASCII||Standard 7-bit ASCII|
|Date||Number of days since January 1, 1998|
|Single||Single-precision floating point|
|ConRes||Constant resolution. This is a custom data type for compressed floating point values that provides a linear mapping of a defined interval|
|ConRelRes||Constant relative resolution. This is a custom data type for compressed floating point values that provides a logarithmic mapping of a defined interval|
|Enumeration||References a defined enumerated data type defined in the template|
ConRes and ConRelRes provide a method of coding non-integer values with minimal bit usage by defining a limited range over which the bits are mapped. The range and resolution for ConRes and ConRelRes properties are listed in the template.
Template 25: Accelerometer and Force Transducers
This template is intended for use with dynamic accelerometers and force transducers which are constant-current pwered, or IEPE.
Template 27: Microphones (with Built-in Preamplifiers)
This template is intended for measurement microphones that include an integrated preamplifier. Typically, these devices will have a constant-current powered, or IEPE, interface.
Templates 26, 28, 29 and 43
Templates 26 and 43 are intended for charge amplifiers, with the provision for describing an attached piezoelectric transducer, either an accelerometer or force transducer. Template 28 is a microphone preamplifier template, which can specify an attached microphone capsule. Template 29 is a template describing a capacitive microphone.
Details for the contents and makeup of templates 26, 28, 29, and 43 are included in Annex A of the IEEE 1451.4 specification.
Template 30: High-Level Voltage Output Template
This template is a general-purpose template designed for use with a very wide range of sensors. Virtually any sensor with an analog voltage output can use this template. The first 6-bit Select Case indicates the physical measurand and the corresponding units (such as PSI, N, m/s2, mm, %, etc.).
Template 31: Current-Loop Output Template
Like the voltage output template, this template is a general purpose template designed for use with a very wide range of sensors. Virtually any sensor with a current loop output (typically 4-20 mA or 0-20 mA) can use this template. The first 6-bit Select Case indicates the physical measurand and the corresponding units (such as PSI, N, m/s2, mm, %, etc.).
Template 32: Resistive-Output Sensors Template
This template is a general-purpose template intended for any sensor whose electrical output is a variable resistance. If a resistive sensor is configured as a potentiometer, template 39 may be more appropriate. The first 6-bit Select Case indicates the physical measurand and the corresponding units (such as PSI, N, m/s2, mm, %, etc.).
Template 33: Bridge Sensors Template
The bridge sensors template is intended for any sensor whose electrical output interface is a resistive bridge with a linear output. For example, this may be a load cell, pressure sensor, or accelerometer. The first 6-bit Select Case indicates the physical measurand and the corresponding units (such as PSI, N, m/s2, mm, %, etc.).
Template 34: AC LVDT/RVDT Template
The bridge sensors template is intended for AC-based linear variable differential transformer (LVDT) and rotary variable differential transform (RVDT) sensors. The first 3-bit Select Case indicates the physical measurand and the corresponding units (such as m, mm, inches, radians, or degrees).
Template 35: Strain-Gage Template
The strain-gage template is intended for strain gauges used in a bridge measurement configuration. While the scaling of readings from the bridge is based on the gage factor, and may or may not be linear, the properties for minimum and maximum physical and electrical ranges are still included to define the operating range of the sensor.
Strain gages are unique in that many of the measurement parameters are determined by how the gages is installed and mounted. Therefore, the template includes more properties that are determined by the measurement configuration and the property to which the gauge is mounted. Examples of this are Poisson's coefficient, Young's modulus, and bridge type .
Template 36: Thermocouple Template
The thermocouple template includes designation of the measurement range, electrical output range, and type of thermocouple. Detailed specification of non-standard thermocouple curves is not included in this template.
Template 38: Thermistor Template
The thermistor template specifies the operation of a thermistor using the Steinhart-Hart thermistor equation.
Template 37: Resistance Temperature Detector (RTD) Template
The RTD template, through the RTD Curve select case, allows the specification of a standard DIN curve (cases 0 through 5) or custom curve (cases 6 and 7) using Callendar-Van Dusen coefficients.
Template 39: Potentiometric-Voltage Divider Template
Tempate 39 is intended for sensors whose outputs are configured as a potentiometer, in a resistive voltage divider configuration. The first 6-bit Select Case indicates the physical measurand and the corresponding units (such as PSI, N, m/s2, mm, %, etc.).