Vescent SLICE-QT User manual

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Product Manuals - https://www.vescent.com/manuals/
SLICE-QTC Four-Channel Temperature
Controller
Model No. SLICE-QT and SLICE-QTC
Document Revision: 1
Document Last Updated on 2022/07/20 23:32
Please read Limited Warranty and General Warnings and Cautions prior to operating the SLICE-QTC.
Links
Click here for the SLICE-QTC Quick Start Guide.
Click here for the SLICE-QTC API.
Click here for the Ziegler-Nichols loop tuning instructions.
Click here for the SLICE-QTC web page.
Click here for the Github page for SLICE-QTC GUI
Click here for the Github page for SLICE-QTC firmware revisions
Please check back for added functionality. Contact sales [at] vescent [dot] com for questions and
corrections, or to request added functionality.
Description
The SLICE-QTC is a high-precision temperature controller (see figure 1). It will control up to four
thermal plants with sub-millikelvin precision.
Fig. 1: The SLICE-QTC
Purchase Includes
SLICE-QTC Temperature Control Unit
AC power cord with appropriate wall plug for you location (if known)
Four single-ended 6-ft control cables1)
Final Test Documentation

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Absolute Maximum Ratings and Power Input
Note: All modules designed to be operated in a laboratory environment.
Parameter Rating
Environmental Temperature >15°C and <30°C
Environmental Humidity <60%
Environmental Dew Points <15°C
Maximum AC Line Input Current 2 A
Tab. 1: Absolute Maximum Ratings
The SLICE-QTC will accept input line voltages within the ranges shown in table 2.
Parameter Value Units
Input Line Voltage 100-240 VAC
Frequency 50-60 Hz
Phase 1 phase
User-serviceable fuse2) T 2.0 A L 250V
Tab. 2: Input Voltage Specifications
Proper Usage
If this instrument is used in a manner not specified by the manufacturer in this
manual or other relevant literature, protection provided by the instrument may be
impaired.
Successful implementation of the SLICE-QTC depends critically on the design of the
whole system: controller, transducer, plant, and sensor.
Tips for Successful Temperature Regulation
The transducer, plant, and sensor must all be in good thermal contact. Use thermal paste or1.
epoxy to avoid air gaps between a TEC or heater and the body of the plant as well as to secure
the thermistor to the plant.
Know the electrical limits of of your transducer and set the limits of the SLICE-QTC accordingly.2.
Each channel can provide up to 6 A or 20 W of power with a maximum compliance voltage up to
~18 V. Choose transducers that work within these limits. Using the current, power, and/or
voltage ratings of your transducer to calculate loads on individual channels and set limits
appropriately in the CH X > Settings > Load Limits window.
Maintain proper shielding of the control cable, but avoid ground loops between the SLICE-QTC3.
and the plant. In most cases this means extending the foil shield in the cable to as close as
possible to the plant without electrically connecting the SLICE-QTC to the plant.
Never connect either of the TEC leads on a plant, or the SLICE-QTC to ground.
This configuration is very likely to cause severe damage to the SLICE-QTC.

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List of Symbols
Warning. Pay special attention to procedures
and notes. If procedure is not followed
carefully, damage to the SLICE-QTC or
devices connected to it may occur.
Potential for electrical shock hazard.
Specifications
Performance3)
Parameter Value
Channels 4
Loop Filter PID, adjustable corners and
proportional Gain
Control Range -10 to +120°C
Compatible Transducer TEC or resistive heater
Compatible Sensor NTC thermistor 4)
Temperature Stability ±0.2 mK over 10 min5)
Precision ~1 mK
Control Capacity 40 W total6)
20 W max for a single channel
Current Capacity 6 A per channel7)
Compliance Voltage ≤18 V8)
Input & Output
I/O Voltage Range ±10 V
Triggering TTL
Control Interface
Control Front-panel touch screen, GUI, Serial
API
Connections Host control: USB Type B
Tab. 3: Specifications of SLICE-QTC
Extendable Legs
The SLICE-QTC has four extendable legs (figure 2). Extending the front legs allows easy viewing from
above (figure 1) and extending the rear legs (figure 3) allows easy viewing from below.

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Fig. 2: Underside of SLICE-QTC
Fig. 3: Side view of SLICE-QTC configured for
viewing from below
Front Panel
An image of the front panel is shown in figure 4. The functions and connections are as follows:
Parameter input adjustment knobs1.
Control signal inputs2.
Signal monitor outputs3.
Touch screen with view of CH 2 Details screen4.
∆T plotted as a function of time (blue line)5.
System locked range (yellow dashed lines)6.
Fig. 4: Front of SLICE-QTC
Rear Panel
An image of the rear panel is shown in figure 5. The functions and connections are as follows:
Main On/Off power switch1.

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AC line power in9) 2.
User-serviceable fuse (T 2.0 A L 250V)1.
Output trigger (BNC)3.
Input trigger (BNC)4.
USB port (Type B)5.
Connections to thermal plants10)11) 6.
Fig. 5: View of rear of SLICE-QTC
Interface Connections
Connections to the thermal plants are made from the rear panel. Four cables for this purpose are
provided with the SLICE-QTC. Each has one end terminated with a CUI Inc. PDP-40 connector for
connecting to the CUI Inc. CP-7240-ND connector on the SLICE-QTC. The other end is unterminated
and is for connecting to your specific plant. The pin out for connecting the cable (Beldon 1502R
010500) to your specific plant is given in table 4.
Connector
Pin Number Color Function AWG
1 Red TEC/Heater+ 18
2 Black TEC/Heater- 18
3 White Thermistor+ 22
4 Blue Thermistor- 22
Metal Sleeve Ground Shield 24
Tab. 4: Cable pinout
Do not have servo loop engaged when
connecting Servo Output to your plant.

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Use caution grounding the shield (drain) at
the transducer end of the interface cable as
ground loops may be formed, degrading
performance. Consider floating the plant or
not connecting the shield to the plant
chassis.
You may purchase more cables separately from Vescent Photonics. We do not recommend making
cables, but if you do so, make sure the metal sleeve is well connected to the connector ground to
provide proper shielding to the signal cables.
Operating the SLICE-QTC
Screen Navigation
The touch screen interface and the Host GUI operate in a substantially similar way, except touch is
substituted for a click in the touch screen interface.
When presented with a given view, it is possible to select the functionality or edit the values in a field
bordered in blue. When a particular field is actively being edited, its border will change to yellow. The
Home Screen of the SLICE-QTC is shown in figure 6. From the Home screen, summary control over the
four channels is possible, including setting Tset, initiating lock, or entering an individual channel's
Detail screen.
In general, the status displayed in an editable field is the current status (not the result of touching the
button). Touch the field to select a new value/status. For instance, in figure 6 all of the channels are in
stand by. Touching the OFF button to initiate servo control over a plant will change this button to read
ON (figure 17).
Fig. 6: Home screen of SLICE-QTC
To navigate away from a menu, it is typically necessary to press the escape button found on that
menu. However, certain drop downs without a escape button, such as those found in the Auto Tune
process, can be closed by touching anywhere on the screen outside of the menu. In general, if the
menu has a escape button on it, the escape button must be pressed to exit the menu.

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Control Bar
On the left edge of the screen is the Control Bar. At any given time, these buttons will have the
following effect.
Home Button
Fig. 7: Home button Returns to Home screen (figure 6).
Back Button
Fig. 8: Back button Returns to previous screen. Changes will be lost if not accepted before using the
Back button.
Lock Button
Fig. 9: Lock button (shown in unlocked mode) Locks out further modification of parameters. Touch to
lock or unlock parameter entry. It is still possible to engage the temperature control loops when
system is locked, but it is not possible to change the set point temperature or loop parameters, etc.
I/O Button
Fig. 10: I/O button Enters the screen for programming the front-panel I/O.
System Settings Button

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Fig. 11: System settings button Enters screen for system control settings (brightness, volume, etc.).
Entering Values
In order to afford maximum resolution, the least significant digit will not necessarily change to
precisely your target value and will be coerced to the nearest acceptable value, which is limited by
the digitization scheme for the set point. For instance, you may select a set point temperature of
17.000°C, but the closest allowed digitized value may be 16.999°C.
In most instances, there are two methods for entering parameter values: the physical rotary knobs on
the front panel and the pop-up keypad on the touch screen. When using the knobs to change the
value of a parameter, changes take effect immediately. When using the keypad, changes do not take
effect until the enter key is depressed.
Rotary Knobs
If you touch an editable field for a brief moment, a cursor will appear under one of the digits of the
parameter value. By turning the right knob, it is possible to increase (cw) or decrease (ccw) the value
of the underlined digit. Turning the left knob will change which digit is editable (cw to move to the
right and ccw to move to the left).
Keypad
If you touch and hold an editable field such as the set point temperature, a numeric keypad will
appear as seen in figure 12. You can enter in the full value of the desired parameter with this keypad.
Fig. 12: Pop-up Keypad
The action initiated by each button is described below.

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Escape
Fig. 13: Escape button Exits keypad without accepting changes.
Clear
Fig. 14: Clear button Clears value in field being edited.
Delete
Fig. 15: Delete button Deletes last character entered.
Enter
Fig. 16: Enter button Accepts edits and exits keypad.
Home Screen
The Home screen summarizes the status of all four channels (figure 6). The data for each channel is
arranged vertically. At a glance, for each channel, Tset, Tact, and ∆T can be read, as well as whether
servo control is engaged. If the loop is engaged and ∆T is smaller than a user-defined range, the Error
value field will be green, indicating a locked state. If ∆T is outside this user-defined range, this field
will turn yellow.
Setting the Temperature
To set the temperature set point from the home screen, touch the Setpoint window for the desired
channel (circled in red for CH 1 in figure 17). A long touch will cause a keypad to appear. Enter

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desired value and touch the accept button.
A short touch will highlight the Setpoint window in yellow (figure 18). Use rotary knobs to select digit
to edit (left knob) and value for digit (right knob).
Fig. 17: Select Temperature setpoint for CH 1
Fig. 18: Knob adjustment of Temperature setpoint for CH 1
Enabling Feedback
Touch the OFF button at the bottom of the column for the desired channel. The button will turn white
and read ON to indicate the SLICE-QTC is actively controlling the temperature for that channel. PID
settings may still need to be input for the SLICE-QTC to servo plant temperature correctly. In figure 17
and figure 18 CH 1 is active and CHs 2-4 are inactive.
As the system approaches lock, it will display ∆T on a yellow background. When the system is locked
(as defined by the user in the CH X > Settings > Limits screen) the Error window will display ∆T with a
green background.
Channel Detail Screen
You can set how individual channels behave in the Channel Detail screen. To enter a Channel Detail

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screen from the Home screen, touch the CH button for the appropriate channel (figure 6). figure 21
shows the CH 1 Detail screen. From this screen, you can change Tset, and initiate temperature control
as from the Home screen. You can also visually monitor the performance of the loop. When the lock is
engaged, the graph in the lower right of the screen displays ∆T (Tact - Tset) on a rolling basis. The yellow
dashed lines indicate the user-defined “lock range” (see figure 24). In figure 21, the lock range is set
to ±3 mK. If ∆T is outside of this range, the Error field background will change from green to yellow.
Change the speed of the rolling display: touch the button and select from 1 to 20 s/div.
Change the scale of the vertical axis: touch the button and select from 1 mK/div to 10
K/div.
Pause and restart the rolling screen: touch the button.
Turn on & off cursors on the graph: touch the button. It is possible to drag the cursors
across the display of ∆T to measure an oscillation period. This function will be helpful when
tuning the loop parameters to your plant.
Adjusting the Graph
To adjust the vertical range (∆T) of the graph, either touch the button and select an option
from the pop-up menu (figure 19), or turn the right rotary knob.
Fig. 19: Menu to adjust y-axis on temperature plot
To adjust the time base (∆t) of the graph, either touch the button and select an option from
the pop-up menu (figure 20), or turn the left rotary knob.

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Fig. 20: Menu to adjust x-axis on temperature plot
Display of Transducer Current, Voltage, and Power
As shown in figure 21, the current being delivered to the transducer is displayed in the blue box on
the right margin labeled Current [A]. If you touch the blue box, the box will rotate through displaying
current through, voltage across, and power delivered to the transducer.
From this screen, you can also set the various parameters for how the loop will behave.
Fig. 21: Initial view of CH 1 Detail screen
Setting Control Modes
Touch the Settings button in the top right of the window. The sub-menu shown in figure 22 will
appear.

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Fig. 22: Menu of settable parameters
Channel Settings
PID Filter and Slew Rate Adjustment
PID Settings
Fig. 23: Screen for adjusting PID parameters for individual channel
To set the PID loop filter parameters from the Home screen, select CH X > Settings > PID Params and
the screen in figure 23 will appear. The parameters for the PID loop filter are set in this popup screen.
These parameters control the closed-loop behavior of the feedback. Each of these parameters will
need to be tuned specifically for your plant, either manually or with the Auto Tune feature. There are
a number of methods to tune a loop. We recommend the Ziegler-Nichols method.12) Instructions on
using this method can be found here. There is also an option to enable or disable each parameter in
the loop filter.

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Slew Rate Limit
For applications where the rate of change of the temperature of the plant needs to be controlled, it is
possible to set an upper limit on the slew rate. This can also be done through the PID Params screen.
Setpoint °C Sets the setpoint temperature of the
plant.
Proportional V/V Sets the proportional gain of the loop
filter.
Integral sec Sets the integral time constant of the
loop filter.
Derivative sec Sets the derivative time constant of
the loop filter.
Slew (Rate) ºC/min Sets the maximum slew rate for the
plant temperature.
Tab. 5: Setting loop parameters
If appropriate, make sure to turn the Slew Rate
Limit off when changing use case!
Maximum & Minimum Temperature, Lock Range
Set Maximum & Minimum Temperature
The maximum and minimum allowable temperatures (Tmax and Tmin) can be set as well as the range of
∆T where the system is considered to be locked. From a Channel Detail screen (figure 21), tap
Settings > Temp Limits and the screen in figure 24 will appear. It is advised to set Tmin above the dew
point temperature for your ambient conditions to avoid condensation on your plant surface. If the
temperature of the plant exceeds the range set by Tmax and Tmin, the temperature will be displayed in a
flashing red field.
Set Lock Range
In the view shown, the lock range has been defined to be ±3 mK. If -3 mK ≤ ∆T ≤ +3 mK, ∆T will be
displayed on a green field. If outside this range, ∆T will be displayed on a yellow field. The graph in
the bottom right of the Channel Detail screen plots ∆T vs. time. The dashed yellow lines on this plot
represent the lock range limits as set in this screen.

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Fig. 24: Menu for setting absolute extrema and lock range
Locked
Range ºC
Defines the nominal operating
temperature range for the plant. When the
actual temperature is within this window
(±value), the temperature error will be
displayed on a green background. When
the error in the temperature is outside this
window, the temperature error will be
displayed on a yellow background.
Maximum
Temp ºC
Sets the maximum and minimum
operating temperatures of the plant. The
user will be prevented from adjusting the
setpoint temperature to outside this
range. If the actual temperature exceeds
this range, the temperature will be
displayed on a flashing red background.
Minimum
Temp ºC
Shutdown
Time s
Sets the delay between when the
temperature goes out of range and when
the SLICE-QTC shuts the current off.
Tab. 6: Warning and Max/Min
If your plant is exposed to the atmosphere, use an abundance of caution in setting Tmin below
the dew point for your ambient conditions! Water will condense on surfaces that are below
the dew point temperature.
Power Limits
The User can limit the control power available to individual channels. To adjust control capacity from
the Home screen, select CH X > Settings > Load Limits and the screen shown in figure 25 will appear.

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Fig. 25: Screen for adjustment of control power capacity
Transducer and Thermistor
To set the properties of the transducer (TEC or heater) and thermistor for an individual channel from
the Home screen, touch CH X > Settings > Plant. The menu in figure 26 will appear. Select
TEC/Bipolar (as seen) or select Heater/Unipolar by touching the TEC/Bipolar button to toggle between
the two.
From this screen, it is also possible to set the polarity of the TEC. Touch Polarity Positive/Polarity
Negative to toggle between the two states. The polarity is already set correctly to NEGATIVE for use
with NTC thermistors.
The thermistor data has been configured at the factory for a typical NTC thermistor that is 10 kΩ at
25°C. Only NTC (Negative Thermal Coefficient) thermistors can be used. You can enter a new Beta
value, reference temperature, and resistance value and the Steinhart-Hart constants will be
calculated automatically or vice versa.
NOTE: The SLICE-QTC can achieve sub-millikelvin stabilities over a very wide set point temperature
range. For most applications working near room temperature, an NTC thermistor with a nominal value
of 10 kΩ at 25°C will work fine. For temperatures far from room temperature, best results will occur
by choosing a thermistor that has a resistance of 10 kΩ at your desired set point temperature. The
input bridge circuitry is configured to have maximum sensitivity at a 10-kΩ resistance.
Fig. 26: Set Thermistor and Plant Information

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WHEN USING A RESISTIVE HEATER, be sure to set the transducer type (CH X >
Settings > Plant) to Heater/Monopolar. If set to TEC/Bipolar, attempts by the SLICE-
QTC to actively cool your plant will result in a thermal runaway condition.
Front-panel Inputs & Outputs
The front panel of the SLICE-QTC has two analog inputs (channels A & B) and two analog outputs
(channels 1 & 2, not to be confused with the temperature control channels) available for use. The two
analog outputs can be configured to output useful monitor signals, while the two analog inputs can be
configured to provide additional functionality. A schematic of the input and output functionality is
shown in figure 29, with the light blue boxes indicating the front panel I/O. The voltage range of the
analog I/O on the SLICE-QTC is ±10 V.
To program the functionality of the front panel I/O, from any screen, touch the I/O icon on the left
sidebar. You will be presented with the screen shown in figure 27.
Fig. 27: Programming the front-panel I/O
Touch the blue-framed window to the right of the I/O channel you wish to program. Upon doing so,
you will be presented with a pull-down menu of the various options available for that channel. For
instance, if you select channel A input, you will be presented with the screen shown in figure 28. You
can select the input to be any of the signals shown in table 7 for any of the four temperature-control
channels.

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Fig. 28: Programming the input on Channel A Input
Each selected function for inputs and outputs will have settings that you can adjust, specific to the
chosen functionality. To access these settings, select the Settings (“gear”) icon that is just to the right
of the selection window. A pop-up window will be presented that displays the various settings that can
be adjusted for that feature.
Fig. 29
Input Channels A & B
External Set Point
In this mode, an external signal can be used to supply the set point temperature of the plant. The set
point temperature is related to the input voltage (Vin) by: Set Point Temp [˚C] = Gain [˚C/V] x Vin +

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Offset[˚C]. Touch the Settings icon to the right of the channel selection to adjust the Gain and Offset.
This mode comes with both an absolute, and relative option, which can be selected separately
through the I/O menu.
External Temperature Input
This mode allows a bypass of the temperature read from a thermistor on a plant to use a temperature
from a device that generates voltage as a function of temperature. The temperature is related to the
input voltage (Vin) by: Temperature [°C] = Gain x Vin + Offset. Touch the Settings icon to the right of
the channel selection to adjust the Gain and Offset.
External Error Input
This mode allows the temperature error to be derived from an external temperature transducer. In
this mode, the thermistor and associated signal processing electronics are not used. The temperature
error is related to the input voltage Vin by: Temperature Error [˚C] = Gain [˚C/V] x Vin + Offset [˚C].
Touch the Settings icon to the right of the channel selection to adjust the Gain and Offset.
Feedforward
This mode allows a feedforward signal to be summed into the output of the PID loop filter. The
feedforward signal current is related to the input voltage Vin by: Feedforward Current [A] = Gain[A/V]
x Vin + Offset[A]. Touch the Settings icon to the right of the channel selection to adjust the Gain and
Offset.
Slow Servo Input
In some use cases, it is convenient to have the temperature set point automatically adjusted to keep
another external parameter (which depends on temperature) at a certain value. For instance, the
frequency of a laser might be controlled by adjusting the cavity length via a piezoelectric transducer
(PZT). Over time, the cavity length may drift outside the range of the PZT, causing the laser to unlock.
In this case, the laser cavity might have its temperature automatically adjusted so as to center the
PZT voltage in the middle of its operating range.
When this mode is active, the input signal is compared with a set point voltage (settable by the user)
to derive an error signal that is input to a single integrator loop filter. The output of the integrator
automatically adjusts the the temperature set point to maintain the input voltage signal at set point
voltage. When the slow servo is enabled for a channel, the temperature setpoint field for that channel
on the home screen will be highlighted blue, as shown in (figure 30).

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Fig. 30: Slow Servo enabled on channel 1
The setpoint temperature of the slow servo channel can still be adjusted, by touching the Setpoint
[°C] field. To adjust the slow servo settings, press and hold on the blue Setpoint [°C] Field. This will
bring up the slow servo menu as shown in (figure 31).
Fig. 31: Slow Servo menu showing adjustable parameters
This can be done either from the home screen or the single channel summary menu. Gain, polarity,
and setpoint can also be adjusted from the I/O menu by pressing the “gear” icon next to the A or B
input where the slow servo is enabled.
Choice Comment
Off Value not read
External Set Point Externally control the set point
temperature
External Temp
Input
Alternate input path for plant
temperature
External Error
Input
Alternate input path for error signal
(bypasses wheatstone bridge)
Feed Forward Sums input value with loop filter output.
Slow Servo Input Input is routed through an integrator and
then used to control the set point
Tab. 7: Front-panel input signals