The ADAM-4011/4011D Thermocouple Input Modules use a microprocessor-con- trolled integrating A/D converter to convert sensor voltage, current or thermocouple signal into digital data. The digital data is then translated into either two’s comple- ment hexadecimal format or percentage of full-scale range (FSR) according to the module’s configuration. When prompted by the host computer, the data is sent through a standard RS-485 interface.
The ADAM-4011/4011D Thermocouple Input Modules offer signal conditioning, A/D conversion, ranging, and RS-485 digital communication functions. They protect your equipment from power surges at the ground terminal by providing opto-isolation of the A/D input and transformer based isolation up to 3000 VDC. (ADAM-4011 has transformer-based isolation up to 500 VDC)
Open Thermocouple Detection and Input Surge Protection (ADAM-4011D only)
The ADAM-4011D provides an open thermocouple detection function. Users can use a simple command to detect whether the thermocouple is opened or closed. The module also provides surge protection on its input channel. Internal high-speed tran- sient suppressor on its input channel protects the module from dangerous spikes and voltages.
Front Panel LED Indicator (ADAM-4011D only)
The 4½ digits LED display on the back of the ADAM-4011D lets you monitor the pro- cess readings right at their source. The module displays readings in a wide variety of formats as well as high-low alarm messages. The ADAM-4011D offers flexibility, easy installation, and direct availability of process data. For critical process monitoring, this module is the ideal choice.
The ADAM-4011/4011D Thermocouple Input Modules also contain two digital outputs and one digital input. Outputs are open-collector transistor switches that may be con- trolled by the host computer. They can control solid-state relays, which may be used to control heaters, pumps, and other electrical powered equipment. The digital inputs may be read by the host computer and used to sense the state of a remote digital signal.
The event counter is connected to the Digital Input channel and can be used to keep track of the total amount of external low-speed pulses. Its accumulated maximal count is 65535. The count will maintain at 65535 even if the actual number of events exceeds 65535. The counter can be read or reset to zero by the host computer.
Since the Event counter’s data are not stored in EEPROM, the event counter is cleared and set to zero after every reset or start up of the analog input module.
Analog input modules include High and Low alarm functions. High and Low alarm limits may be downloaded into the module’s EEPROM by the host computer.
The alarm functions can be enabled or disabled remotely. When the alarm function is enabled, both Digital Output channels are used to indicate the High and Low alarm state. Digital Output channel 1 (DO1) equals to High alarm state, and Digital Output channel 0 (DO0) equals to Low alarm state. The High and Low alarm states can be read at any time by the host computer.
Every A/D conversion will be followed by a comparison with the High and Low limit. When the input value exceeds one of these limits, the High or Low alarm state is set to ON.
There are two alarm mode options, Momentary and Latching. If the alarm is in Latch- ing mode, the alarm will stay on even if the input value returns within the limits. An alarm in Latching mode can be turned OFF by giving a Clear Alarm command from the host computer. A Latching alarm is cleared by the module when the opposite alarm is set. When the module receives a value that is lower than the Low alarm limit, it will clear the High alarm and turn the Low alarm ON.
When the alarm is in Momentary mode, the alarm will be turned OFF as soon as the input value returns within the limits. The arrangement of coupling High and Low alarm states with Digital Output lines may be utilized to build ON/OFF controllers that can operate without the involvement of host computer.
Function Description for the ADAM-4011 Thermocouple Input Module
To provide a better understanding of the ADAM module functions, the following is a description of the module ADAM-4011 with the most extensive set of functions.
All analog input data first flow through the PGA (programmable gain amplifier). The amplifier can vary its gain from 1 to 128. The PGA then automatically adjusts the sig- nal to a range from -2.5 V to +2.5 V.
This ensures an optimal input voltage and resolution for the A/D converter.
The A/D conversion is supervised by the microprocessor that holds the calibration software. Two kinds of calibrations, Auto Zero and Auto Span calibrations, take place automatically in startup or reset. Normal calibration is used to adjust the signal according to calibration parameters defined by the user.
The digital 10 Hz filter provides a steady state output by using the ∆ function.
Before the data enter the microprocessor, they pass through an optical isolation device which prevents the chance of circuit damaging caused by power surges from the ground terminal.
The microprocessor has six basic functions:
- Linearization of T/C (Thermocouple)
- Communication software and command set
- Calibration software
- Alarm monitoring
- Event counting
- Management of the EEPROM device that holds the system parameters
- Data transformation
After data have been transformed to the right data format, they are being passed on to the RS-485 output port.
If an input value exceeds the High alarm setting or falls below the Low alarm setting, a flag is set in one of the Digital Output channels.
Finally, the on-board switching regulator accepts voltage between +10 and +30 VDC, and it has an isolation value of 500 VDC to protect your equipment from damages caused by power surges.