LB-718T Digital Thermometer with a Resolution of 0.01°C and Modbus RTU Support

• Air temperature (or other medium)
• robust and dust-proof housing
• Wide operating temperature range
• RS-485 interface, MODBUS RTU
• temperature resolution of 0.01°C
• PC software - LBX Server (SCADA-type)
  

Description

The LB-718T digital thermometer is designed for air temperature measurement in rooms or other media in the version with external temperature sensor (TX). It may operate in extremely dusty spaces, thanks to the use of air-tight housing and suitable filter protecting the measuring sensor. It is a small, stationary thermometer, powered by an external source. Measurement data are displayed on a two-line LCD display; they may be displayed with a resolution of 0.01°C.

To make the measurements, the thermometer uses data from the external Pt-1000 temperature sensor. On the basis of the known non-linear characteristics of the temperature sensor and digital calibration data stored during calibration on the device storage memory, the built-in microprocessor calculates the current temperature measurement results. The results are available in a digital form for the supervising data collection system via the RS-485 interface and MODBUS RTU protocol.

The LB-718T thermometer is equipped with a digital RS-485 interface that allows the operation of up to 32 devices on one rail with a total length of up to 1,200 m. Thethermometer integrates the widely-known MODBUS RTU protocol, thanks to which the thermometer may operate in many systems based on this standard. In particular, the LB-718 thermometers may be connected via the DE-311 Ethernet converter with the LBX software, serving as a central point of the LAB-EL monitoring system.

The thermometer is equipped with jumpers used for setting the MODBUS address in the range of 1…32.

The output of the LB-718T digital thermometer is made with screw clamps (4 camps — power, A and B lines), located inside the housing, to which a cable is led through an opening with a diameter of 7 mm.

The thermometer does not feature mechanical calibration elements (e.g. potentiometers). The thermometer calibration includes sending calibration data via a digital interface to the instrument’s permanent storage, obtained from the calibrated climatic conditions. It ensures convenience and high calibration accuracy as well as the stability of the device's metrological parameters over time.

The LB-718T digital thermometer may come in a special "S" version (poured with siliconic compound), which makes the electronics resistant to high levels of humidity. Irrespective of the ("S") version, the instrument may not be subject to direct atmospheric precipitation nor water vapour condensation.

The standard version of the thermometer (without siliconic compound) is fitted for short-term (up to a few hours) measurements within the measuring range limits. In addition to the measurements, the device is to be kept in the recommended continuous operating conditions. In the standard version, the instrument is equipped with a sensor screen (impurities filter), type F3.

Calibration certificates

Each digital thermometer, as per order, may feature an individual calibration certificate provided by LAB-EL Calibration Laboratory.

Dedicated software

This thermometer may additionally come with an advanced software for Windows — the LBX software — enabling:

• presentation of current readings from devices;
• alarm monitoring and signalling;
• presentation of archived data — charts, reports, histograms;
• data archive management;
• access for remote clients.

Technical Data

TEMPERATURE MEASUREMENT
Measurement uncertainty	±0.1°C (1)	in the range of 50°C
	±0.2°C (1)	in the range of 100°C
	±0.4°C (1)	in the range of 200°C
	±1.5°C (1)	in the range of 400°C
	±3.0°C (1)	in the range of 750°C
Measurement range	-40…+85°C
	-100…+260°C (2)	TX version
	-200…+550°C (2)	TXE version

Remarks:
(1) Additionally, ±1 last digit
(2) For the LB-718TX/TXE, the actual measurement range: may be limited by the functionalities of the temperature probe. E.g.: -60…+90°C for standard TL2 probe.

MEASUREMENT READING
Parameter	Reading range	Resolution
Temperature	-200.00…+550.00°C	0.01°C via digital RS-485 interface
	-200.0…-100.0°C and +100.0…+550.0°C	0.1°C on the LCD display
	-99.99…+99.99°C	0.01°C on the LCD display

RECOMMENDED CONTINUOUS OPERATING CONDITIONS *)
Temperature range	0…40°C
Humidity range	20…80%

*) Exceeding the recommended continuous operating conditions (e.g. when installing the device outdoors) requires the use of additional protective measures for the electronic part of the device against the eventuality of water entering the device (protection of the electronics with silicone or usage of additional external housing).

POWER SUPPLY, MECHANICAL DATA
Voltage range	7…28 V DC
Power consumption	approx. 4 mA	without a terminator
External dimensions of the housing	170 x 64 x 35 mm
Material	plastics (polymas, ABS)
Housing protection class	IP 65	additionally limited by the protection class of the filter

DIGITAL INTERFACE

RS-485 transmission parameters: 19,200 bps, 8 information bits, parity control — Even, 1 stop bit (19200/8E1) or (configured with a jumper starting with the firmware v1.0.1) 9,600 bps, 8 information bits, no parity control — none, 1 stop bit (9600/8N1)

MODBUS RTU protocol. Interface connection in the form of 4 screw clamps, accessible after removing the device’s cover. Address set with jumpers in the range of 1…32.

Description of available MODBUS registers

INPUT REGISTER (READ SINGLE/MULTIPLE REGISTER)
The value defined as the register address is the same as the one that should appear in the Modbus data package in the address field. Sometimes the PC software adopts the Modicon convention and requires that the input register address be expanded by 30001 more than the value given in this document — e.g. the DEVID register would then have 30001.
Address	Designations	TYPE	Description
0	DEVID	WORD	Device type identification 0x0718 (hex format)
1	CPTB	WORD	Firmware version from the viewpoint of operation via MODBUS. In the event that the user’s software recognises firmware of a newer version (FVER register) than the supported one, it should — while reading this register (CPTB) — confirm that it is able to support the device. The version specified in the CPTB register is possibly the oldest version that the current firmware is backward compatible. Description correct for CPTB = 10000.
2	SNUM	WORD	Serial number of the device
3	FVER	WORD	Firmware version in the form of X.Y.Z, where: X — tens of thousands of FVER, Y — hundreds of FVER, Z — units of FVER. E.g.: for FVER = 21203, it is 2.12.3
4	CONFIG	WORD	The value of a variable set by the manufacturer; meaning of bits: 0: humidity measurement present 1: thermometer featuring wide range of temperature (E version: -200…+550) 2: temperature measurement averaging enabled (for the FLOAT type variable) 3: humidity measurement averaging enabled (for the FLOAT type variable) 4: temperature resolution of 0.01°C
5	STATUS	WORD	State of the device; meaning of bits: 0: ERROR_T — temperature measurement error 1: ERROR_RH — humidity measurement error 2: CFG_ERR — calibration error Remaining bits feature no meaning
6.7	T	FLOAT	Temperature
8.9	RH	FLOAT	Humidity
10	T_WORD	WORD	Temperature as a number in U2 code with a resolution of 0.1°C (the read-out value should be divided by 10)
11	T_WORD_AVG	WORD	Temperature — the same as above, but averaging
12	RH_WORD	WORD	Humidity as a number in U2 code with the resolution of 0.1% (the read-out value should be divided by 10)
13	RH_WORD_AVG	WORD	Humidity — the same as above, but averaging
14	CAL_YM	WORD	Date of the last calibration, LSB: year — 2000, MSB: month
15	CAL_DH	WORD	Date of the last calibration, LSB: day, MSB: hour
16	CAL_M	WORD	Date of the last calibration, MSB = 0, LSB: minute

DEVICE IDENTIFICATION
Read Device Identification 43/14 BASIC ID

EXTENSIONS

By special order, the following set-ups are available:

• The LB-718TS digital thermometer of increased resistance to climatic conditions (in siliconic compound).
• The LB-718TFn digital thermometer — version of sensors’ cover (according to description), the version is given if it is not F3.
• The LB-718TX digital thermometer — fitted for connecting an external temperature sensor.
• The LB-718TXE digital thermometer — fitted for the connection of an external temperature sensor working in the range of -200…+550°C.

INTERACTION WITH THE DE-311 ETHERNET CONVERTER

LB-718T devices may be connected to the DE-311 converter, thanks to which the measurement data may be monitored by the LBX software via Ethernet.
Connection of the LB-718 with the DE-311 should be made according to the following table:

DE-311	LB-718T	DC 7…28 V power unit	Signal description
3	A		Data + (B)
4	B		Data - (A)
5	-	-	Power - / GND
	+	+	Power +

Microswitch of the DE-311 converter should be in the RS-485 position:

SW1	SW2	SW3
OFF	ON	ON

Other versions of the LB-718 thermometer

• LB-718 digital thermometer/hygrometer