LI-19

read-out unit
&datalogger
with µV sensitivity
v 5.1

Introduction
The LI-19 is a low-cost, high-performance sensor readout unit with integrated datalogger.
The sensor sensitivity can be programmed into the LI-19 such that the readout will show
calibrated engineering units, rather than millivolts or microvolts.
Use of the datalogger functions and programming the sensor sensitivity, requires a USB
interface which is used to connect the LI-19 to a PC.

Specifications
A/D conversion
Input range (programmable)

Basic accuracy after factory calibration
Temperature sensitivity
Offset drift
Operation temperature range
Storage temperature range
Relative humidity
Input circuit
Input low-pass filter
Input connectors
Display
Decimal dot position (programmable)
Display update
Computer interface
Supply currentBatteries
Battery life (alkaline)
Data logger memory
Data logger storage interval
Logged information
Software compatibility

Full scale voltage+/- 200 mV+/- 100 mV+/- 50 mV+/- 25 mV+/- 12.5 mV+/- 6.25 mVInternal counts
20,00010,0005,000
25,00012,5006,250

16 bits
Internal resolution
10µV
10µV
10µV
1µV
1µV1µV

0.1%< 0.5% over the full temperature range< 3 µV over the full temperature range-10 .. +40 °C-20 .. +60 °C< 95% RH non-condensing> 2 MΩ // 680 nF
5 Hz
2 x 4mm banana plug
LCD 4 digits with sign
8888 or 888.8 or 88.88 or 8.888
At least 1 per second
USB 1.1 / 2.0 low speed< 2 mA
2 AA (penlight) alkaline> 600 hours (25 days) continuous use
3518 samples
2 .. 65535 seconds
Min, max and average over log interval
Windows 2000, Windows XP, Windows VistaOperation
The LI-19 accepts two AA size (penlight) batteries. Use alkaline types for best results. New,
good quality batteries should give up to 50 days of continuous operation.
Remove the bottom cover of the enclosure to access the battery compartment. Extract thebattery holder from the compartment, and install two fresh batteries. Notice the polarization.
Replace the bottom cover and connect the sensor. The LI-19 is now ready for use. Switch theLI-19 on with the push-button switch on the top.

To prevent that the LI-19 is switched off while logging, the on/off switched is mounted so thatthe button has to be pressed quite deep to switch the LI-19 on or off. You can feel it and hear
it when the switch toggles. Press the small black button far enough with your nail or a pencil
until you feel and hear it switch.

Software
Use of the sofware requires a PC with Windows (Vista or newer) operating system and a USB
interface. The software has built-in functionality for:-programming the sensor sensitivity-

data logging functions

For each of these functions, an interface cable is required. This cable is used to connect a LI19 to the USB bus on a PC. If your LI-19 comes bundled with a sensor, it may be that yoursupplier already programmed the sensor sensitivity into the LI-19, and that this function isdisabled in the software. In that case, the optional interface cable and the software give youaccess to the data logging functions only.

Main window
After installation, the software can be started from the Start menu. The main window allows
you to open a previously stored file with logged data.

LI-19 window

All other functions related to the LI-19 are available in special windows, that will open once
you connect an LI-19 to the PC. You can connect more than one LI-19 to your PC, and foreach of the devices a separate window will open. These windows may be on top of eachother, move them around on your screen to reveal the ones that are covered.
Note that the buttons for ‘Sensor settings’ may not be available on your version of thesoftware.

The PC will automatically detect the LI-19. If the PC does not detect the LI-19, then check if
the LI-19 is switched on, and check the batteries.
Once the LI-19 is detected, the caption of the window will show the serial number of the LI-19
that was connected.

Programming the sensor sensitivity
The software is used to program the sensor sensitivity into the LI-19. If the LI-19 came
bundled with a sensor, your supplier may already have programmed the sensitivity of thissensor into the LI-19. If that is the case, the software you received may not have this option.

WizardYou can use the built-in wizard to determine optimal settings for the LI-19, depending on thetype of sensor that you have, and its calibration factor.

Depending on the sensor sensitivity, the Wizard will select the optimal input stage
amplification for the LI-19, and store appropriate settings for the input amplifier. The positionof the decimal dot in the display is also set. After the wizard is used, the LI-19 only has to be
programmed to make it suitable for use with the specified sensor.
Use the ‘Select sensor’ button to access the wizard. The Wizard accommodates manydifferent sensors.

Use the wizard to select the sensor model that is to be used, and then enter the sensitivity ofthe sensor. The LI-19 is then ready to be programmed with the new settings. To do that, clickthe ‘Program’ button.
Once programmed this way, the LI-19 shows the sensitivity for a few seconds on the display
when switched on, before it starts showing actual measurements. This way you can check thesensitivity setting before use.
Please note that the LI-19 only shows the sensitivity when programmed using the PC
software at least once – so it may not yet do this when you receive the unit.

ManuallyYour version of the software may not have manual selection of the input amplifier enabled. If it
is enabled, and if you want to manually enter the sensor settings, the required LI-19 setup isdetermined in the following steps:
1. Go to the ‘Sensor settings’ page. The full range output voltage of the sensor shouldbe less than or equal to the full scale input voltage of the LI-19. The full range output
voltage is used to select the maximum input stage amplification factor of the LI-19 in
the software. In the box that says ‘Input amplifier’ you can select the amplification that
corresponds to the required full scale input.
2. Next to the amplification factor, you can read how many internal counts each input
range will give you. The number that the LI-19 should display at the full scale input
value is entered into the multiplier input field. The number of internal counts that
corresponds to that full scale input, is entered into the divider field.
3. The decimal dot position for the display is selected.
4. Tick the ‘Allowed’ checkbox for negative values if the sensor can measure values lessthan zero. If you do not tick this box, the LI-19 will clip all negative values to zero.
5. The LI-19 is ready to be programmed with the new settings. To do that, click the‘Program’ button.
Some examples:
We have a sensor with a calibration factor of 1.238 mV/W/m2. We want to measure in a testroom where the light intensity is 100 W/m2 max.
Step 1: Set the input amplifier to give the required range. Select the ‘Sensor settings’ page.

The full scale output of the sensor is:
1.238 mV/W/m2 x 100 W/m2 = 123.8 mVThis should fit the selected range, so an amplification of 1x (input range 200 mV) is the rightchoice. From the table you can see that this range gives you 20000 counts.
Step 2: Determine the display reading. Enter the figure that the LI-19 should display at fullscale in the multiplier field. You can use all 4 available digits, keeping in mind that we can add
a decimal point later. So in this case we can enter 1000 for the multiplier.
Enter the number of counts that correspond with the full scale output of the sensor (here20000 counts * 123.8mV / 200mV = 12380 ) in the divider field.
Step 3: Set the decimal dot to 888.8. The display will then read 100.0 at 100 W/m2 input onthe sensor.
Step 4: Select if you want to see negative values or not.
Step 5: Program the settings into the LI-19.
One more example.
We have a sensor with a calibration factor of 4.56 μV/W/m2. We want to measure in the open
field where the maximum expected irradiance is 1100 W/m2.
Step 1: Set the input amplifier to give the required range. Select the ‘Sensor settings’ page.
The full scale output of the sensor is:
4.56 μV/W/m2 x 1100 W/m2 = 5.016 mVThis should fit the selected range, so select an amplification of 32x, that gives an input range
of 6.25 mV. From the table you can see that this range gives you 6250 counts.
Step 2: Determine the display reading. Enter the figure that the LI-19 should display at fullscale in the multiplier field. You can use all 4 available digits, keeping in mind that we can add
a decimal point later. So in this case we can enter 1100 for the full scale display value in themultiplier field.
Enter the number of counts that correspond with the full scale output of the sensor (here 6250
counts * 5.016mV / 6.25mV = 5016 ) in the divider field.
Step 3: Set the decimal dot to 8888. The display will then read 1100 at 1100 W/m2 input on
the sensor.
Step 4: Select if you want to see negative values or not.
Step 5: Program the settings into the LI-19.

Data logger
The PC software is used to enter the data logger setup, and to transfer the setup to the LI-19.
When the LI-19 is programmed with a new datalogger setup, the logger memory in the LI-19
is erased, and then the new settings are used to start a new logging sequence. The logging

only stops when the logger memory is full, when the batteries are depleted, or when the LI-19
is switched off. The PC software can be used to check the logging activities of the LI-19, andthe LI-19 also shows some display characters to indicate what it is doing.

Log interval
The log interval is entered in seconds. The pull-down box can be used to preset the correct
number of seconds for some popular log intervals. Note that the pull-down is only used forselecting a preset, the number on the left is the log interval that will be transferred to, andused by, the data logger in the LI-19.

Initial delay
When logging starts, an optional delay is used to postpone the start of the first logging interval
until a specified date and time. This date and time at which the first interval will start, can beentered in the PC software. When the logger is busy counting down the delay for the firstlogging interval, the LCD on the LI-19 shows an ‘l’ that flashes at a slow ( 1 second on, onesecond off) rate.

Logging
Once the initial delay has elapsed (the initial delay can be 0) the first logging interval isstarted. The LI-19 is now actually logging, and the ‘l’ on the LCD flashes rapidly ( ½ secondon, ½ second off)

Logged values
During a logging interval, the LI-19 accumulates minimum input value, maximum input value,
and average input value. Once the logging interval has elapsed, the values are stored in thelogger memory and the next interval is started. Each time the LI-19 stores a new set of values
in the logger memory, it flashes the ‘m’ sign on the display. Logging only stops when thelogger memory is full, when the batteries are depleted, or when the LI-19 is switched off.

Read status
You can view the logger status while the logger is active. Reading the status will not interferewith the logging process.
The status will show what the logger is doing, how much time remains in the current interval(if the logger is logging) and what the measured values are. The logger measures an integral
over the logging interval. The PC software uses the integral and the interval period tocalculate an average value over the logging interval.

Read data
Use the PC software to read the logger memory from the LI-19. You can do this while the LI19 is logging, reading data will not interfere with the logging process. When the data from thelogger memory is collected, it will be presented in a chart.

The Y scale can be manually set, and you can also use the mouse to zoom in on a specificarea of the chart. Drag the mouse pointer from the top left corner of the area of interest, to thebottom right corner of the area of interest. When the mouse is released, the chart will zoom inon the selected area.

Drag the mouse from bottom right to top left to zoom out again.
Save the data in a logger data file, or export the data in a text format that can be imported in aspreadsheet.
Use the Copy button to place the chart on the clipboard, ready to be pasted into a word
document.

Leiderdorp Instruments
Dijkgravenlaan 17
NL 2352 RN Leiderdorp
The Netherlands
Phone: +31-71-5415514
Fax: +31-71-5418980
e-mail: info@leiderdorpinstruments.nl
www.leiderdorpinstruments.nl