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Part: 485DTT
Category:
Interface and Interconnect
Description: Digital Thermometer & Thermostat With Rs-485 Interface
Company: B&B Electronics
Datasheet: Download 485DTT datasheet File size : 83 kB
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Datasheet text preview:
Documentation Number 485DTT1795 - pg. 1/2
Not Recommended for New Installations.
Please contact Technical Support for more information.
Digital Thermometer & Thermostat with RS-485 Interface
Model 485DTT
B&B Electronics' 485DTT is an inexpensive digital thermometer and thermostat which operates through an RS-485 interface. Non-volatile registers hold programmable high and low thermostat settings. Current temperature is reported by polling the DTT, while thermostat operations continue as long as the unit is powered. The RS-485 interface allows multiple units to communicate up to 4000 feet on a single pair of wires.
Features
· · · · · · ±0.5°C accuracy and resolution High, low and hysteresis type thermostat outputs Port-powered from host RS-232 port (RTS & DTR high) Thermostat thresholds programmable in non-volatile registers Latching Status Register indicates which thermostat outputs have tripped Programmable node address and turn around delay allows up to 255 nodes to be multidropped
Specifications
Communications Standard: Baud Rate: Format: Connector: Optical Isolation: RS-485 two or four-wire 1200 to 9600 (automatic detection) 8 data bits, 1 stop bit, no parity DB-25S (female), RS-530 pinouts TD(A) - 2, TD(B) - 14, RD(A) - 3, RD(B) - 16, GND - 7 If optical isolation is required, use B&B's 485HSPR high-speed optically isolated converter with this product.
Thermometer Error ±0.5°C from 0 - 70°C ±1°C from -40°C to 0°C and 70°C to 85°C (±1.8°F from -40°F to 32°F and 158°F to 185°F) (The 485DTT is guaranteed to operate from 0-70°C) Thermometer Resolution: 0.5°C Temperature Conversion Time: 1 second Open Collector Thermostat Outputs Low (on) voltages: 1.2Vdc @ 100 mA max. High (off) voltages: 40Vdc max. Power External power: 12VDC @ 25mA
© B&B Electronics -- January 1995
Documentation Number 485DTT1795 - pg. 2/2
Not Recommended for New Installations.
Please contact Technical Support for more information.
485DTT Functions
Digital Thermometer The 485DTT continuously measures temperature, with a new measurement completed once per second. When a Read Temperature command is received, the DTT immediately reports back the result of the last measurement completed, using 9-bit, two's complement format. The ninth bit is the sign bit. If this bit is a 0, the temperature is above 0°C. If the bit is 1, the temperature is less than 0°C. Each bit represents 1/2°C. Programmable Thermostat The 485DTT also functions as a thermostat. Two non-volatile registers can be programmed. The high threshold register, TH, is programmed using the !0SH command. The low threshold register, TL, is programmed using the !0SL command. Thermostat operation is a continuous background function. As long as the unit is powered, the thermostat outputs will be serviced. Three open collector outputs provide thermostatic controls. These outputs are current sinking (low) when on, high impedance (high) when off. 1. THIGH - Turns on when the temperature equals or exceeds the user programmed TH register. 2. TLOW - Turns on when the temperature is equal to or less than the user programmed TL register. 3. TCOM - Turns on when the temperature equals or exceeds the TH register and turns off when the temperature is equal to or less than the TL register. This output allows the user to program any amount of hysteresis.
485DTT Commands
The DTT commands can be issued from a program, or even typed in from a simple terminal program. Two files are included on the 485DTT disk to help learn the DTT commands. A sample program with source code written in QuickBASIC 4.5 demonstrates all DTT functions and a simple terminal program is also included. In addition, a simple data logging utility is provided which allows data to be logged to a file. Command Summary Command Argument !0RT none !0RS none !0RH none !0RL none !0SC none !0SH 9 bit, 2's comp. !0SL 9 bit, 2's comp. !0SA new address char (1 byte) !0SD number of chars delay (1 byte)
Function read temperature read status register read high thermostat read low thermostat clear status register set high thermostat set low thermostat set 485 address set turn around delay
Return Value 9 bit, 2's comp. byte 9 bit, 2's comp. 9 bit, 2's comp. none none none none none
© B&B Electronics -- January 1995
Others parts begin by 48
48-1 48-2
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