OPERATING INSTRUCTIONS
Connections
The Model 311 accurately simulates and reads 2, 
3, or 4 wire RTDs. Press the 2, 3, 4 WIRE pushbutton to match the instrument being calibrated. 
All connecting wires must be the same length and 
of the same material running along the same path 
to insure maximum accuracy.
Two, Three or Four Wire
Two wire RTD measurements are less accurate 
than other RTD measurements because of the 
errors introduced by the resistance of the lead 
wires. The third wire in a three wire hookup provides the instrumentation with a reference connection for the lead wires. The measuring instrumentation uses this reference to infer the actual 
resistance of the RTD element without the leads. 
Four wire RTD measurements take into account 
all wires other than the RTD sensing element. 
This makes four wire RTDs best suited for precision measurements.
Compatibility with Excitation Currents
RTD measuring instruments use different levels of 
excitation current to read RTDs. The 311 operates 
with excitation currents from 0.090 to 10.20 mA. 
As the excitation current increases the highest 
resistance that can be simulated decreases. With 
currents from 0.090 to 1.2 mA the 311 can simulate up to 2000Ω. At 5.00 mA of excitation the 
highest simulated resistance is 500Ω and at 10.20 
mA the highest simulated resistance is 250Ω.
Some transmitters, recorders and other RTD input 
devices use intermittent, or pulsed, excitation currents to measure the resistance of the RTD. The 
Model 311 may be configured to operate with both 
fixed excitation currents (default operation) and 
with intermittent currents as fast as 56 milliseconds (see User Options below).
Changing RTD Types
Eleven RTD types or ohms may be selected to 
match the sensors and instruments in your plant. 
The symbol Alpha (α) is used to identify the particular RTD curve. The value is derived by dividing 
the resistance of the sensor at 100°C by the resistance at 0°C (α = R100°C/R0°C). For Pt 100 
DIN/IEC/JIS this is 138.50/100.00 = 1.3850. This 
value is sometimes represented as 0.00385 or 
simply as 385.
To change RTD types:
1) Turn the selector knob to the desired Metal (Pt, 
Cu, Ni or to Ohms. Note that for the most 
common RTD type, Pt 100Ω DIN/IEC/JIS α =
1.3850, there is a dedicated position on the 
selector.
2) For Pt and Ni sensors there are a choice of several α values. Press the SETUP push-button to 
scroll through the available α curves. 
Note: The Pt 200Ω, 500Ω & 1000Ω curves are 
not available when Intermittent Current 
Compatibility is enabled.
Changing Batteries
Low battery is indicated by BAT on the LCD display. Approximately 10 hours of operation remain 
before the LCD goes blank and the Model 311 
shuts itself down. Turn the Model 311 off, loosen 
the screw on the battery compartment and lift off 
the battery compartment door. Replace the six 
“AA” batteries, replace the door and tighten the 
screw.
Auto-Off
The 311 can be set up to turn itself off after 30 minutes of inactivity. The 
internal timer is reset to 30 minutes each time the digital pot is turned or 
a push-button is pressed. This configuration is part of the DEFAULTSETTINGS.
Enabling Intermittent Excitation Current Compatibility
The 311 may be configured to operate with instruments that use only constant excitation currents or with a mix of instruments that use constant or 
intermittent excitation currents. This configuration is part of the DEFAULT 
SETTINGS.
Configuring Temperature Scales
The 311 may be configured for full time use of °C, full time use of °F or 
selectable °C and °F operation. This configuration is part of the DEFAULT 
SETTINGS.
Selecting Autoranging or 1° Resolution
The Model 311 may be configured to autorange or to constantly display 
with fixed resolution. When autoranging is selected, the Model 311 will 
display temperatures with 0.1° or 1° resolution. When fixed range is 
selected, the Model 311 will display temperatures with 1° resolution.This 
configuration is part of the DEFAULT SETTINGS. 
Note: Some ranges are always displayed with 1° resolution.
General
User Options
DEFAULT SETTINGS - USER OPTIONS
The 311 may be restored to the factory settings. This will reset the HI,SET 
and LO “QUIK-CHEK” memories for all RTD types to 0 °C (32 °F) and the 
Ω range to 100Ω. Prompts also guide you for selection of Auto-Off, 
Intermittent Current Compatibility, temperature scale(s) and resolution.
1) Press and hold the STORE/RESETpush-button while turning the 31 1 on.
2) Keep pressing the STORE/RESET push-button until the display 
flashes (about 5 seconds) then release.The revision number of the 
firmware will be displayed for a few seconds.
3) After five seconds the words SETUP, BAT and on will appear on the 
display indicating that AUTO-OFF is selected.
4) To toggle the AUTO-OFF function on and off press the SETUP pushbutton and the words on and OFF will display.
5) After five seconds the 311 will automatically store your choice and the 
words SETUP, OFF and a symbol for pulsed current (a waveform) will 
display indicating that Intermittent Current Compatibility is off.
6) To toggle Intermittent Current Compatibility on and off press the 
SETUP push-button and the words on and OFF will display.
7) After five seconds the 311 will automatically store your choice and the 
word SETUP, and the symbols °C & °F will display.
8) Press the SETUP push-button to make your selection. With °C 
flashing the unit will only display in °C, With °F flashing the unit will 
only display in °F and with both flashing you can select °C and °F for 
each T/C & RTD type. °C/°F is selected if no push-buttons are 
pressed.
9) After five seconds the 311 will automatically store your choice and the 
word SETUP and 0.1° will appear on the display.
10)To toggle the resolution press the SETUP push-button to switch 
between 0.1° and 1°.
11)After five seconds the 311 will automatically store your choice and the 
311 will begin normal operation.
Pt
Cu
Ni
Ω