MODEL 309 FOUR CHANNEL DATALOGGING THERMOMETER
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4.0 Operating Instructions:
4.1 Preparation for Measurement
Plug as many thermocouples as are to be monitored into the sockets marked T1 through
T4, taking care to observe the polarity of the thermocouple pins. If a differential
measurement is required, this is available only between T1 and T2, which determines
which thermocouples should be connected to these locations.
4.2 Pow er and Backlight
The button tu rns both the thermometer and the display backlight
ON or OFF. Press it once to turn the thermometer ON. Every
subsequent momentary press toggles the backlight ON or OFF.
Press and hold this button for 3 seconds to turn the power OFF.
When first powered on, the display will show how much memory
space is available for use, as shown to the right.
4.3 Selectin g the Temperature Scale
When first turned on, the instrument defaults to reading in Celsius (°C). The instrument
toggles between Celsius (°C) and Fahrenheit (°F) each time the °C/°F button is pressed.
The instrument remembers the scale setting when last turned off and powers on in that
setting the next time.
4.4 Data-Hold Operation
The present reading is held on the display by pressing the HOLD button. Pressing the
HOLD button again releases the hold function and returns the instrument to
continuous reading.
In the HOLD mode, the T1-T2, MAX MIN and °C/°F buttons are disabled, as indicated by
two continuous beeps when pressed.
4.5 T1-T2 Operation
When the T1-T2 button is pressed, the display will indicate 1
–
2
indicating the instrument is in the differential mode of T1 minus T2.
The display then indicates T1 value on the top left, T2 value on the
bottom left, and the difference T1-T2 on the bottom right.
4.6 Clock Setup
To set the real time clock:
1. Press and hold the T1-T2 button and then power on the meter.
2. Press HOLD (clock).
3. Press REC (n) or °C/°F (p) to increase or decrease the
number; press HOLD to advance to the next item. The
adjusting order is: year; month; day; hour; minute. Press HOLD
again after the last setting to complete the process.
To abort during a setup process, press the button.
4.7 Recordi ng Interval Setup
To set the recording interval:
1. Press and hold the T1-T2 button and then power on the meter.
2. Press MAX MIN (interval).
3. Press REC (n) or °C/°F (p) to increase or decrease the
number; press MAX MIN to advance to the next item. Press
MAX MIN again after the last setting to complete the process.
To abort during a setup process, press the button.
MODEL 309 FOUR CHANNEL DATALOGGING THERMOMETER
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TX RX GND

4.8 Recording Data
Each momentary press of the REC button will alternately start and
stop recording. To clear the memory, power off the meter, press
and hold the REC button followed by the button, holding both
on simultaneously for at least 5 seconds. The display will show
‘CLR’ ‘SURE 5’, and releasing all buttons then clears the memory.
4.9 MAX/MIN Operation
Press the MAX MIN button to enter the MAX/MIN mode. In this mode, both the maximum
and minimum values are simultaneously retained in memory and updated with every new
data sample. The instrument first enters the MAX mode, and the MAX symbol and value
are both displayed. Pressing MAX MIN again advances the display to the MIN symbol
and value. The next press of the MAX MIN button will cause both the MAX and MIN
symbols to flash. This indicates that the maximum and minimum values have been
updated in memory and the displayed reading is the present temperature. Each
successive press of the MAX MIN button circulates the display mode among these
options. To exit the MAX/MIN mode, press and hold the MAX MIN button for
two seconds.
In the MAX/MIN mode, the °C/°F button is disabled, as indicated by two consecutive
beeps if pressed.
4.10 Auto Power Off
By default, the instrument powers on in the ‘Auto Power Off’ mode and will automatically
shut off 30 minutes after the last key operation or RS232 communication.
To disable this feature, press and hold the HOLD button and then power on the meter.
Two successive beeps will indicate that ‘Auto Power Off’ is disabled, and the will not
be displayed.
4.11 Low Battery Condition
When the battery voltage is at or below the minimum for proper operation, the
symbol will show on the display indicating that the battery must be replaced.
4.12 Calibration
Calibration is conducted by adjusting the following potentiometers to within the
tolerances shown.
(Ambient Temperature: 23 ± 3°C)
Input Adjust VR Tolerance
0 °C VR1 ± 0.1 °C
190 °C VR2 ± 0.1 °C
1000 °C VR3 ± 1 °C
1900 °F VR4 ± 1 °F
4.13 Digital Output
The Digital Output is a 9600 bps N 81 serial interface.
RX is a 5V normally high input port.
TX is a 5V normally high output port.
Appendix: Thermocouple Probe Specifications
Model Range Tolerances Description
TP-K01
Wire probe
-50°C to 200°C
-58°F to 392°F
±2.2°C or ±0.75%
±3.6°F or ±0.75%
Teflon insulation. Maximum insulation
temperature: 260°C (500°F)
TP-K01:
Probe for general condition measurements, especially
for complex and hard to reach places.
A
simple single point calibration may be
performed by adjusting VR1 to 0 °C with
thermally stabilized ice water.