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THT-LCD   Humidity Logger

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The THT-LCD is a handheld humidity datalogger with an external humidity and temperature probe and a liquid crystal display. Both Relative Humidity and Dew Point can be displayed and logged. There are two external Humidity/Temperature probes available for the THT-LCD.

The HT11-Probe uses a Sensirion SHT11 digital humidity sensor giving ± 3.5%RH accuracy from 10%RH to 90%RH.

The HT15-Probe uses a Sensirion SHT15 digital humidity sensor giving ± 2%RH accuracy from 10%RH to 90%RH.

This logger is designed for indoor use (IP 40). For outdoor applications, we recommend mounting the THT-LCD in a TruTrack Seahorse Logger Enclosure.

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Humidity Sensor:
Probe Plug


The probe is connected to a socket on the end plate at the top of the logger.
The probe cable is 1.5 metres.

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Normal Accuracy
Sensirion SHT11
Digital humidity sensor
Long-term stability
Fully calibrated by Sensirion
Response time 4 seconds
Range 0%~100%
Accuracy ± 3.5%RH from 10% to 90%
Accuracy ± 5%RH from 0% to 10% and 90% to 100%
Resolution 0.1%RH
Digital temperature sensor accuracy ± 0.4º C @ 25º C
High Accuracy for
both Humidity and
Sensirion SHT15
Digital humidity sensor
Long-term stability
Fully calibrated by Sensirion
Response time 4 seconds
Range 0%~100%
Accuracy ± 2%RH from 10% to 90%
Accuracy ± 3.5%RH from 0% to 10% and 90% to 100%
Resolution 0.1%RH
Digital temperature sensor accuracy ± 0.3º C @ 25º C
Filter The sensor is covered in a Sensirion SF1 Filter cap. The filter cap provides protection against water, dust and other contaminants for the humidity and temperature sensor.  The filter cap consists of a single piece of polypropylene including a filter membrane.  The filter provides filtration efficiency of 99.99% of all 0.1µ m particles and has an optimized response time of typically 30s (1/e (63%) slowly moving air).
Dew Point:
Sensor Type The Dew Point is calculated from the current Relative Humidity and Temperature
Accuracy ± 2º C (this is determined by the ± 3.5%RH accuracy of the humidity sensor
Resolution 0.1º C
Internal Logger Temperature:
Sensor Type Thermister
Linear accuracy over range ± 0.3º C (0º C to 70º C)
Repeatability ± 0.1º C
Long term stability ± 0.1º C
Working Temperature -20º C to +70º C
Storage Temperature -30º C to +70º C
Sampling Rate
1 second minimum
10 hours maxium
in 1 second intervals
Storage capacity
522,240 samples logging Relative Humidity only 
362 days with 1 min logging interval (Relative Humidity only)
4.9 years with 5 min logging interval (Relative Humidity only)
174,080 samples logging Relative Humidity Dew Point and Temperature
Two independent Alarms
Triggered on any combination of six user configurable Alarm Conditions
Both alarms can be configured to send SMS messages
Two Open Collector Alarm outputs
Alarms can be visually checked on the LCD Display or by using the Omnilog Software
Start modes
Start immediately
Start on date/time
Start on condition (eg Humidity < 30%RH)
Start on trigger (push button on logger)
Stop modes
Stop when memory is full
Stop on date/time
Loop around (continues logging)
Logging Modes
Each channel can be set to log any combination of: 
  • Point readings
  • Average reading
  • Maximum reading
  • Minimum reading
User Replaceable
Two 3.6V Lithium AA cells
One to Five years depending on usage. 
The data is retained in the case of battery failure.
Battery Status Monitor on LCD display and in OmniLog Software
Download Time 9min 30sec for Full Logger
Case material ABS Plastic
IP Rating 40
Weight 185g
Size 130mm x 80mm x 30mm
Mini Din Pinout.jpg (47562 bytes)The THT-LCD has a 8 pin Mini-DIN female socket.

Pin 1  Common
Pin 2  RS232 RX (out of logger)
Pin 3  RS232 TX (into logger)
Pin 4  RS232 CTS (out of logger)
Pin 5  RS232 RTS (into logger)
Pin 6  Alarm 1 Open Collector Output
Pin 6  Alarm 2 Open Collector Output
Pin 8  Power 5 to 16V DC

A DLC8 download cable is required to connect the THT-LCD to a computer

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Liquid Crystal Display Operation

The THT-LCD displays logger status and alarm status continuously and can be set to show the humidity, dew point, probe temperature, internal temperature, the battery voltage and the number of logged samples.

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 Logger status is shown as:



                     Waiting (Waiting for “Start on Condition”)

                     Waiting Trigger (Waiting for “Start on Trigger”)

If the logger is waiting for “Start on Trigger” it can be started in the field from the Menu provided on the display.

 If an Alarm has been triggered the display will show

                     Alarm 1

                     Alarm 2

If both Alarms are triggered “Alarm” will be displayed
continuously and “
1” and “2” will flash consecutively.

 Low Batt will be displayed if the internal batteries requires

THT-LCD Menu Options

Pressing the Enter button on the front panel of the THT-LCD
activates the Menu Display. The
Down Arrow can then be used to scroll down through the various Menu Options. When the required menu option is displayed, press Enter to select this option. Menu Options on the THT-LCD are:

                     Channel 1 (Display Relative Humidity)

                     Channel 2 (Display Dew Point)

                     Channel 3 (Display Probe Temperature)

                     Channel 4 (Display Internal Temperature)

                     Channel 5 (Display Battery Voltage) 

                     Samples (Display number of samples logged)

                     Trigger (IF logger is waiting for Start on Trigger)

                     Alarm 1 (Reset/Trigger) Trigger is used to test

                     Alarm 2 (Reset/Trigger) the Alarms

                     º C / º F toggle

The display will update at 1 second intervals for 1 minute after any button is pushed. It will then slow down to 10 second display updates (this is a power saving feature).

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