LF-TD - air humidity and temperature transmitters

LF-TD air humidity and temperature transmitters

LF-TD is a series of permanently installed transmitters that measure relative humidity and temperature continuously and pass the result to a controller, a data logger or the plant network. The devices work in laboratory and air-conditioning technology, in drying, in the timber, food and feed industries, in construction, in printing and papermaking, in agriculture and in biotechnology and pharmacy.

All models share the same electronics housing and the same way of mounting. What separates them is the length and material of the sensor tube, the permitted temperature of the measured medium and the interface through which they deliver the result.

Which LF-TD model to choose

Two things decide: the temperature at the measuring point and the way the result is to reach the higher-level system. The table below covers all the variants in the 2026 price list.

Model	Art. no.	Sensor	Temperature range	Output
LF-TD-TA	14771	stainless steel Ø12 × 125 mm	-20 to +60 °C	4-20 mA for humidity and temperature
LF-TD 60	12609	plastic Ø12 × 100 mm	-20 to +60 °C	4-20 mA, optionally RS232, USB, Ethernet
LF-TD 90	12665	stainless steel Ø12 × 125 mm	-20 to +90 °C	4-20 mA, optionally RS232, USB, Ethernet
LF-TD 120	12655	stainless steel Ø12 × 500 mm	-20 to +120 °C	4-20 mA, optionally RS232, USB, Ethernet
LF-TD 150	12667	stainless steel Ø12 × 750 mm	-20 to +150 °C	4-20 mA, optionally RS232, USB, Ethernet
LF-TD 180	12938	head on a 1 m cable, cap Ø12 × 35 mm	-40 to +180 °C (sensor head)	4-20 mA, optionally RS232, USB, Ethernet, Profinet
LF-TD-E	13082	plastic Ø12 × 100 mm with a filter	-20 to +60 °C	Ethernet (RJ45 socket)
LF-TD Profinet	14555	stainless steel Ø12 × 125 mm, head on a 0.25 m cable	-20 to +90 °C	4-20 mA and Profinet (RJ45 socket)
LF-TD-H	14601	probe for bulk material	0 to +40 °C	4-20 mA for water content and temperature

The LF-TD-H stands apart in this table: it measures not the humidity of the air but the water content of wood chips and bulk materials, over a range of 2 to 20 % water content, with a resolution of 0.1 % and 0.1 °C.

Data common to the series

Relative air humidity	0 to 100 %
Humidity calibration	±2 % over the range 10 to 90 % (LF-TD-TA: ±3 %)
Temperature calibration	±0.3 °C over +10 to +60 °C (LF-TD-TA: ±0.6 °C)
Humidity output	4 to 20 mA corresponding to 0 to 100 % (except the LF-TD-E)
Temperature output	4 to 20 mA corresponding to the range of the given model (except the LF-TD-E)
Operating temperature of the electronics	-20 to +85 °C (LF-TD-TA: -20 to +60 °C)
Dimensions of the electronics housing	70 × 32 × 120 mm (LF-TD-E: 214 × 76 × 70 mm)
Power supply	12 to 29 VDC (LF-TD-TA: 12 to 24 VDC; LF-TD-E: 5 VDC 300 mA through a USB mini B socket; LF-TD-H: 24 VDC, 15 to 29 VDC)
Protection class	IP 40 for the LF-TD-E electronics housing

Scope of delivery

LF-TD transmitter with a 1.9 m connecting cable ending in a moulded five-pin connector
LF-TD-TA: transmitter with a 1.9 m connecting cable
LF-TD-E: the transmitter alone, without a cable and without a power supply unit

Interfaces

The LF-TD 60, 90, 120, 150 and 180 models leave the factory with the standard 4-20 mA output, and a digital interface is chosen for them separately. The LF-TD-E has Ethernet built in, the LF-TD Profinet a Profinet socket next to the analogue output.

Art. no.	Description
12807	RS232 interface for the LF-TD
12808	USB interface for the LF-TD
13738	Ethernet interface for the LF-TD
12809	Profinet interface - for the LF-TD 180 only
12464	USB plug-in power supply 5 VDC 2.1 A, input 90-250 VAC, EU plug - for the LF-TD-E only (art. no. 13082)

Extended accessories

Art. no. 10006 - calibration set for the tube probe
Art. no. 10352 - certified calibration ampoules, set of 5 at 50 % relative humidity
Art. no. 10005 - certified calibration ampoules, set of 5: 2 at 35 %, 1 at 50 % and 2 at 80 % relative humidity
Art. no. 13731 - display with a keypad for the LF-TD
Art. no. 10249 - stainless steel sensor cap with a sintered filter - for high temperatures and demanding conditions
Art. no. 13799 - nickel-plated sintered bronze sensor cap
Art. no. 12456 - drip guard for the LF-TD transmitter
Art. no. 13612 - angle bracket for the LF-TD
Art. no. 10403 - factory calibration certificate - the adjustment protocol supplied before delivery
Art. no. 12011 - special order, flat rate for the air humidity transmitter series, regardless of the quantity ordered
Art. no. 14711 - HumiSenseWare LF-TD - standard Live Trend licence - requires one of the interfaces: RS232 (art. no. 12807), USB (art. no. 12808) or Ethernet (art. no. 13738)
Art. no. 14712 - HumiSenseWare LF-TD - data management and logging option
Art. no. 14713 - HumiSenseWare - integration package for three additional sensors

LF-TD or huminode IoT RH

Both solutions measure air humidity and temperature continuously, but they fit different installations. The LF-TD is a wired transmitter: it is powered from the installation, mounted permanently and wired straight into a controller or the plant network by a 4-20 mA signal, over Ethernet or over Profinet. It works where there is cabling and where the temperature of the measured medium reaches 180 °C.

The huminode IoT RH, in turn, is a battery-powered wireless sensor that sends its measurements over LoRaWAN to a gateway and on to a dashboard in the browser. It needs no cables pulled, so it suits buildings, warehouses and sites with no installation. An order covers a minimum of five units, and a gateway and a dashboard licence are needed to run it.

Humidity transmitter LF-TD