PiezoDrive PDUS210 User manual

PDUS210 V5 Manual 1 Modified 17/12/2022
PDUS210 - 210 Watt Ultrasonic Driver
Manual and Specifications
Hardware Version 5
Revision History
Date
Revision
By
Changes
16/12/22
2
KB
Public document created

PDUS210 V5 Manual 2 Modified 17/12/2022
Contents
1Introduction .................................................................................................................................. 3
2Safety Warnings ............................................................................................................................ 3
3Delivery Contents .......................................................................................................................... 3
4Quick Start Recommendations ...................................................................................................... 4
5Electrical Specifications ................................................................................................................. 4
6Standard Output Voltage Ranges................................................................................................... 4
7Unipolar Output Voltage ............................................................................................................... 6
8Mechanical Specifications ............................................................................................................. 7
9PDUS210-FLEX Specifications......................................................................................................... 8
10 Introduction to Ultrasonic Transducers....................................................................................... 9
11 PDUS210 Operation.................................................................................................................. 10
12 Control of Vibration Amplitude................................................................................................. 12
13 Choosing the Voltage Range ..................................................................................................... 14
14 Front Panel ............................................................................................................................... 15
15 Rear Panel ................................................................................................................................ 17
16 Overload Protection ................................................................................................................. 18
18 Desktop Software ..................................................................................................................... 19
19 Rack Mounting.......................................................................................................................... 28
20 Warranty .................................................................................................................................. 28

PDUS210 V5 Manual 3 Modified 17/12/2022
1Introduction
The PDUS210 is a complete solution for driving and analysing ultrasonic actuators up to 210 Watts.
Functions include high-speed resonance tracking of both series and parallel resonance modes,
vibration amplitude control, pulsed excitation, frequency modulation, and analysis functions such as
impedance and frequency response measurement. The PDUS210 is well suited to both OEM product
integration and laboratory use for research and development. Applications include ultrasonic drilling
and cutting, cleaning, medical devices, dental devices, ultrasonic testing, cavitation, and vaporization.
The PDUS210 can be controlled from multiple sources including a PC and the included software
package, front panel controls, and/or external logic signals from a foot switch for example. An API for
external controllers is also available for RS485 and USB connections, which are suitable for automatic
test applications and embedded industrial machinery.
The PDUS210 generates a pure sine-wave output which is ideal for operating at the electrical parallel
resonance, or ‘anti-resonance’. This operating point is close to the mechanical resonance frequency
but is less sensitive to changes in load dissipation, which is useful in precision machining applications
where constant vibration amplitude is desired. Current and power control are also available for
regulating vibration amplitude at the series resonance mode.
The PDUS210 is available with standard output voltage ranges from 17 Vrms to 282 Vrms, and current
ranges from 0.7 Arms to 11 Arms. These ranges are optimized for load impedances ranging from 1.5
Ohms to 400 Ohms at resonance. For research and development applications, a reconfigurable
version is available (PDUS210-FLEX), this version uses external output matching transformers to allow
operation at any of the available output voltage ranges.
2Safety Warnings
This product produces potentially lethal voltages up to 282 Vrms.
Observe Low-Voltage safety precautions (as per ANSI C84.1-1989), e.g.
●Use an observer trained in low-voltage rescue
●Do not operate with exposed conductors
●Use appropriate signage
3Delivery Contents
•PDUS210 Amplifier (in chosen configuration)
•IEC Power cable suited to the destination shipping address
•USB Cable (Type A to Type B)
•3-Way plug-in screw terminals for RS485 signals (Amphenol TJ0331530000G)
•4-Way plug-in screw terminals for output signals (Amphenol TJ0431530000G)

PDUS210 V5 Manual 4 Modified 17/12/2022
4Quick Start Recommendations
Most users should read this document in full. However, users with expert knowledge of ultrasonic
transducers and operating modes, may go straight to Error! Reference source not found.
5Electrical Specifications
Specification
Value
Notes
Output Voltage
0 –800 Vp-p
See standard voltage ranges
Output Current Max
0 –32 Ap-p
See standard voltage ranges
Load Impedance
1 –5 k
See standard voltage ranges
Output Waveform
Sine wave
DC Output Voltage
Zero
DC bias voltage on request
Output Isolation
Isolated output
Grounded is also possible
Max Output Power
210 W
With optimal load impedance
Internal Power Dissipation
150 W
Maximum
Frequency Range
See table below
6kHz to 500kHz with modifications
Power Supply
100 Vac –250 Vac
IEC Connector
Controller
Phase tracking
Resonance or anti-resonance
Interface
USB, RS485, Logic
Software APIs are available
6Standard Output Voltage Ranges
The specifications for fixed output models are listed below.
Order Code
Voltage
RMS
Voltage
pk-pk
Amps
RMS
Amps
pk-pk
Optimal
Load (󰇜
Load Range
Ohms [1]
Frequency
kHz
PDUS210-800
282
800
0.71
2
400
260 –840
20 –200
PDUS210-600
212
600
0.92
2.6
225
146 –472
20 –200
PDUS210-400
141
400
1.4
4
100
65 –210
20 –200
PDUS210-200
70
200
2.8
8
25
16 –52
20 –200
PDUS210-175
62
175
3.2
9.1
19.1
12 –40
10 - 100
PDUS210-100
35
100
5.7
16
6.25
4 –13
20 –200
PDUS210-50
17
50
11.3
32
1.56
1 - 3
20 –200
[1] The load impedance range is the range of impedances which guarantee more than 100W of power
supplied to the load. Higher or lower impedances can be driven but with reduced power.
The relationship between maximum achievable power and the load impedance is plotted in the
following figure. In this plot, the impedance is normalized by the optimal impedance; that is,

PDUS210 V5 Manual 5 Modified 17/12/2022
 

For example, the optimal impedance of the PDUS210-400 is 100 Ohms, so with a 50 Ohm load, the
normalized impedance is 0.5, From the plot, it can observed that greater than 100 W can be achieved
with a normalized impedance from 0.65 to 2.1, which for the PDUS210-400, is 65 Ohms to 210 Ohms.
Figure 1. Maximum output power versus normalized impedance
The impedance ranges for other common power levels are listed in the following table. For example,
all amplifiers will supply more than 150W with a normalized load impedance between 0.71 and 1.4.
For the PDUS210-400, this is equivalent to 71 Ohms and 140 Ohms.
Minimum Power
 Lower Bound
 Upper Bound
150W
  
  
100W
  
  
50W
  
  
Table 1. Minimum achievable power versus load impedance.

PDUS210 V5 Manual 6 Modified 17/12/2022
7Unipolar Output Voltage
The output voltage of a standard PDUS210 or TX210 device is bipolar. For example, the maximum
output voltage of the PDUS210-200 or TX210-200 is +/-100V. The PDUS210 and TX210 can also be
configured with a positive or negative unipolar output range using the order code suffix
–UnipolarPositive or –UnipolarNegative. For example, the order code PDUS210-200-UnipolarPositive
or TX210-200-UnipolarPositive would result in a maximum output voltage range of 0V to +200V, as
shown in Figure 2.
The unipolar option adds a DC offset voltage which is equal to half the signal amplitude; therefore,
the resulting voltage is always between zero volts and the chosen amplitude, as shown in
Figure 2. Compared to a fixed DC offset voltage, this approach minimizes the average DC voltage,
which improves transducer lifetime.
Since the output of the standard PDUS210 and TX210 is electrically isolated, the polarity of the offset
voltage can be inverted by reversing the connection of the transducer to the amplifier or transformer.
In other words, except for very specific applications where the phase of the output voltage is
important, the –UnipolarPositive option can be used to create both positive and negative offset
voltages by reversing the polarity of the transducer connection.
Figure 2 Comparison of standard bipolar output voltage and unipolar output options.
Standard Bipolar Output
Positive Unipolar Option
Negative Unipolar Option
Full Output
Half Output

PDUS210 V5 Manual 7 Modified 17/12/2022
8Mechanical Specifications
The mechanical specifications of the enclosure are listed below.
Specification
Value
Notes
Dimensions [1]
212 x 304.8 x 88 mm (8.35 x 12 x 3.46 in)
L x W x H
Mass
2 kg (4.4 lb)
Temperature
0C –50 C (32 - 122 F)
Humidity
Non-condensing
Ingress Protection
No dust or water ingress protection [2]
[1] A 3D Model is available at www.piezodrive.com
[2] The PDUS210 requires clean room air for cooling.

PDUS210 V5 Manual 8 Modified 17/12/2022
9PDUS210-FLEX Specifications
The PDUS210-FLEX is identical to the standard PDUS210 except that it requires an external
transformer connected between the amplifier and transducer using the supplied cable. This allows
the user to switch between different output voltage ranges by changing the external transformer. For
operating instructions, please refer to PDUS210-FLEX Operation.
The PDUS210-FLEX must be purchased with at least one external transformer. The default output
configuration is electrically isolated with a bipolar voltage. Refer to Unipolar Output Voltage for other
options. The available part numbers and specifications are:
Order Code
Turns
Ratio
Voltage
RMS
Voltage
pk-pk
Amps
RMS
Amps
pk-pk
Optimal
Load
Load Range
Ohms [1]
Frequency
kHz
PDUS210-800
18.18
282
800
0.71
2
400
260 –840
20 –200
PDUS210-600
13.64
212
600
0.92
2.6
225
146 –472
20 –200
PDUS210-400
9.09
141
400
1.4
4
100
65 –210
20 –200
PDUS210-200
4.55
70
200
2.8
8
25
16 –52
20 –200
PDUS210-175
3.98
62
175
3.2
9.1
19.1
12 –40
10 - 100
PDUS210-100
2.27
35
100
5.7
16
6.25
4 –13
20 –200
PDUS210-50
1.14
17
50
11.3
32
1.56
1 - 3
20 –200
Table 2. External transformer specifications (only for the PDUS210-Flex)
A kit containing five transformers is available (TX210-Kit1), which consists of the following voltage
ranges: 35 Vrms, 70 Vrms, 141 Vrms, 212 Vrms, and 282 Vrms.
Figure 3. Output transformer (e.g. TX210-800)
Specification
Value
Notes
Input Connector
Plug-in screw terminal
Cable supplied with PDUS210-FLEX
Output Connectors
Identical to PDUS210
See Front Panel
Transformer Dimensions
104 x 57 x 51 mm
L x W x H
Mass
0.2 kg
Table 3. External transformer mechanical specifications

PDUS210 V5 Manual 9 Modified 17/12/2022
10 Introduction to Ultrasonic Transducers
An introduction to the behaviour and operation of ultrasonic transducers can be viewed at
•https://www.piezodrive.com/ultrasonic-drivers/intro-ultrasonic/
Please familiarize yourself with these concepts before operating the PDUS210.
The most important concept to understand is the relationship between the electrical and mechanical
impedance response of a transducer. Figure 4 plots the mechanical and electrical frequency response
of an ultrasonic transducer.
The impedance minima at 
is known as the series resonance, which is approximately equal to the
mechanical resonance frequency. At this frequency, the impedance phase response has a high
positive slope and a value of approximately zero degrees. In this mode, the current is approximately
proportional to the vibration amplitude, so current control is used to maintain constant vibration
amplitude. If the mechanical load does not vary significantly, constant voltage amplitude is also
appropriate.
The impedance maxima at 
is known as the parallel resonance, which also has an electrical phase of
approximately zero degrees but a high negative slope. In this mode, the voltage is approximately
proportional to the vibration amplitude, so constant voltage results in approximately constant
vibration amplitude regardless of mechanical load variations.
Figure 4. Electrical and mechanical frequency response of an ultrasonic transducer

PDUS210 V5 Manual 10 Modified 17/12/2022
11 PDUS210 Operation
11.1 Overview
The operating principle of the PDUS210 is summarized in Figure 5. The transducer on the right is
connected to the output transformer. The transformer converts the internal +/-24V drive voltage to
the desired output voltage range, for example +/-200V. By default, the output connection to the
transducer is electrically isolated from ground but the negative output can also be internally
grounded using the jumper shown.
During operation, the voltage and current in the transducer is used to estimate the phase . The
measured phase is then used to control the frequency of the signal generator by comparing it to the
phase set point . The frequency controller stabilizes the feedback loop and controls the settling
time of the closed loop system. The feedback gain is normally determined experimentally by slowly
increasing the gain until the desired performance is reached or the response begins to become
unstable.
The signal generator has a variable amplitude, and the frequency is normally controlled by the phase
control loop. It is connected to the power amplifier, which drives the output transformer and
transducer.
Figure 5. PDUS210 operation (in constant voltage, resonance tracking mode).
11.2 Resonance Tracking
The resonance tracking system of the PDUS210 is illustrated Figure 5. The phase detector measures
the impedance phase angle between the primary voltage and current. The frequency controller 󰇛󰇜
varies the drive frequency to maintain a constant phase set point , which is usually equal to zero.
To operate at a series resonance (impedance minima), the phase controller gain must be positive to
create a stable operating point.
Signal
Generator
Phase
Setpoint
Frequency
Controller
Power
Amplifier
Transformer
Transducer
Ground
Connection
Phase Detector

PDUS210 V5 Manual 11 Modified 17/12/2022
To operate at a parallel resonance (impedance maxima), the phase controller gain must be negative
to create a stable operating point.
Applications with high losses, i.e. low quality factor, may have a non-zero impedance phase angle at
resonance, e.g. 45 degrees. In such cases, an impedance response should be performed first, to
identify the desired operating phase that corresponds to the desired mechanical resonance.

PDUS210 V5 Manual 12 Modified 17/12/2022
12 Control of Vibration Amplitude
Power ultrasonic applications can be categorized as either constant mechanical load, or variable
mechanical load. The requirements for both cases are described in the following.
12.1 Constant Mechanical Load
Constant load applications are the simplest case and include, for example, ultrasonic cleaners,
ultrasonic mixers, and any other application where the mechanical load does not vary significantly.
These applications can be operated with constant voltage at either the series or parallel resonance.
12.2 Variable Mechanical Load
Applications with variable mechanical load include ultrasonic drills and cutters where the mechanical
load conditions vary during operation. These applications generally require some form of amplitude
control to maintain vibration amplitude when the mechanical load dissipation increases; and to avoid
vibration amplitude increasing when the mechanical load dissipation is reduced.
To achieve approximately constant vibration amplitude, a transducer can be driven with constant
voltage at the parallel resonance frequency, or constant current at the series resonance frequency.
Constant voltage is the natural operating mode of the PDUS210 but constant current can also be
achieved by enabling the current tracking mode. The operation of current tracking mode is illustrated
in Figure 6. Current tracking mode has the same frequency control loop as Figure 5 but also has an
additional feedback loop that varies the voltage to maintain a constant load current. The current set
point is  and the controller is .
Current tracking mode is most useful for achieving constant vibration amplitude in transducers
operated at the series resonance mode (impedance minima).
Figure 6. Phase and current control loop in the PDUS210 driver.
Signal
Generator
Phase
Setpoint
Frequency
Controller
Power
Amplifier
Transformer
Transducer
Ground
Connection
Phase and Current Detector

PDUS210 V5 Manual 13 Modified 17/12/2022
12.3 Power Control
When operating with constant voltage or current, a limit can be set on the maximum power
dissipation in the load. This power is the sum of dissipation in the mechanical load and the transducer
itself.
In some applications, such as welding and cleaning, it may be preferable to control the dissipated
power rather than the vibration amplitude. The PDUS210 has a power control function that varies the
voltage to maintain a constant power dissipation in the load. As shown in the Figure 7, the power
control loop includes the power measurement which is compared to the power set-point . The
gain of the controller is tuned experimentally to provide a fast transient response and stability.
Figure 7. Phase and power control loop in the PDUS210 driver.
Signal
Generator
Phase
Setpoint
Frequency
Controller
Power
Amplifier
Transformer
Transducer
Ground
Connection
Phase and Power Detector

PDUS210 V5 Manual 14 Modified 17/12/2022
13 Choosing the Voltage Range
The PDUS210 is available in voltage ranges from 17 Vrms to 282 Vrms, which suit load load
impedances ranging from 1.5 to greater than 400 . The optimal choice is determined by the
transducer impedance at resonance, and the choice of series or parallel resonance. If the load
impedance is unknown, or a range of load impedances are expected, the PDUS210-Flex configuration
is recommended with the transformer kit (TX210-Kit1), please refer to PDUS210-FLEX Specifications.
To determine the ideal voltage range, start by measuring the impedance of the transducer at the
series and parallel resonance. This can be performed with an impedance analyser or simply a signal
generator and oscilloscope. If possible, these tests should be performed at moderate power with
both minimum and maximum load conditions. A PDUS210 driver is ideal for performing this
measurement. Fill out the values in the table below:
Unloaded
Fully Loaded
Series Resonance
:
:
Parallel Resonance
:
:
Table 4. Operating impedance at resonance
13.1 Series Resonance
For operation at the series resonance, the most suitable amplifier has an optimal impedance which is
close to, or slightly greater than the fully loaded impedance. Since transducer impedance tends to
increase with applied power, an amplifier with a higher optimal impedance is recommended. If the
amplifier has a higher optimal impedance than the load, the current limit will be reached before the
voltage limit, and the maximum achievable output power is:
  

where  is the maximum driver current.
13.2 Parallel Resonance
For operation at the parallel resonance, the most suitable amplifier has an optimal impedance which
is close to, or slightly less than the fully loaded impedance. Since transducer impedance tends to
reduce with applied power, an amplifier with a lower optimal impedance is recommended. If the
amplifier has a lower optimal impedance than the load, the voltage limit will be reached before the
current limit, and the maximum achievable output power is:
  



where 
 is the maximum driver voltage.
13.3 Custom Voltage Range
Custom voltage ranges and impedance-matching network design is available on request.

PDUS210 V5 Manual 15 Modified 17/12/2022
14 Front Panel
Indicator
Description
Standby
Indicates that the output is enabled but not active
Phase Lock
The measured phase is within +/-10 degrees of the phase setpoint
Output
Output is enabled
Power
Power is on
Temp
A thermal overload has occurred, enable the amplifier to restart
Load
Load power has exceeded the limit, enable the amplifier to restart
Amp
Amplifier dissipation has exceeded 150W, enable the amplifier to restart
Supply
Supply current limit has been exceeded, enable the amplifier to restart
Voltage Range
Output voltage, relative to maximum voltage limit
Current Range
Output current, relative to maximum current limit
Amp Range
Amplifier power dissipation, relative to 150W
Load Range
Load power dissipation, relative to maximum power limit
Control
Function
Momentary On
Output is active while pressed
Amplitude
Amplitude control, “Use Remote Amplitude”must be enabled in software
On / Off
Toggles the output between active and standby
Shutdown
Disables the output
Power
Turns the power on

PDUS210 V5 Manual 16 Modified 17/12/2022
Connector
Description
USB
Connection to PC, requires a Type A to Type B cable (included)
RS485
RS485 interface, suits Amphenol TJ0331530000G connector
Control
External logic control, see notes [1]
Screw HV Output
Suits Amphenol TJ0431530000G connector, see notes [2]
LEMO HV Output
Suits LEMO 0B.302 Connector (e.g. FGG.0B.302.CLAD42)
[1] The amplifier can be controlled by external logic signals, such as foot switches etc. The signal
connector is a 9-way DSUB receptacle, which suits any 9-way male DSUB plug. The signals and pin
layout are shown in Error! Reference source not found. and Error! Reference source not found..
Figure 8. Front view of control signals connector
Signal
Pin
Function
3.3V Power
1
3.3V Power from the amplifier. 20mA maximum current. Unprotected.
Amplitude
2
Remote amplitude control. 0V to 2.9V maps to 0 to 100%. Zin = 500 .
Momentary
3
Identical to pressing the momentary button. 3.3V logic.
Status 0
4
For future assignment, will be used to indicate amplifier status. 3.3V logic.
Shutdown
5
Identical to pressing the shutdown button. 3.3V logic.
Ground
6
Ground, also connected to the connector shield. Connected to IEC earth.
Status 1
7
For future assignment, will be used to indicate amplifier status. 3.3V logic.
Connected
8
Connect this to pin 1, used to indicate the presence of an external controller
On-Off
9
Identical to pressing the on/off button. 3.3V logic.
Table 5. Control signals pinout
[2] The transducer is connected between HV+ and HV-, which are electrically isolated from ground.
The transducer can be grounded remotely, or by connecting either HV+ or HV- to the Ground pin. The
TX ID pin is reserved for future use, this is a low-voltage pin aimed at communicating calibration
information with external transformers.
1
2
3
4
5
6
7
8
9

PDUS210 V5 Manual 17 Modified 17/12/2022
15 Rear Panel
The rear panel consists of an IEC C14 mains power inlet (100 Vrms to 250 Vrms) and an air inlet.

PDUS210 V5 Manual 18 Modified 17/12/2022
16 Overload Protection
16.1 Temperature Overload
•Triggered when the heatsink temperature exceeds 60C.
•The output will be disabled, and the Temp indicator will light.
•An enable command is required to clear the overload.
•Check the fan and heatsink for blockages.
16.2 Load Power Dissipation Overload
•Triggered when the load power dissipation exceeds the defined limit.
•The output will be disabled, and the Load indicator will light.
•An enable command is required to clear the overload.
•Increase the Load power limit, or reduce the output amplitude.
16.3 Amplifier Power Dissipation Overload
•Triggered when the amplifier power dissipation exceeds 150 W.
•The output will be disabled, and the Amp indicator will light.
•An enable command is required to clear the overload.
•Reduce the output amplitude and check he transducer impedance.
16.4 Supply Hardware Overload
•Triggered when the internal power supply is overloaded.
•The output will be disabled, and the Supply indicator will light.
•An enable command is required to clear the overload.
•Reduce the output amplitude and check the transducer impedance.

PDUS210 V5 Manual 19 Modified 17/12/2022
17 Desktop Software
17.1 Installation
Download the latest software from www.piezodrive.com and run the executable, which will extract
the desktop software to the selected folder. Go into the folder and launch the executable
(piezodrive.exe). Ignore operating system warnings about security, this software does not have a
windows security certificate. However, this will be added in future releases.
17.2 Firmware Update
The desktop software will automatically download the latest compatible version of the firmware;
thus, it is import to check for new desktop software periodically at:
https://www.piezodrive.com/ultrasonic-drivers/pdus210-ultrasonic-driver/
17.3 Offline Firmware Update
Manually download the latest firmware. Also download the latest version of the desktop software.
The procedure for a manual firmware update is:
1. Turn the amplifier power on while holding the red shutdown button. This places the amplifier in
update mode and the front panel indicators will display a flashing pattern.
2. Open the desktop software and ensure the amplifier is connected by a USB cable.
3. Open the settings page and click the Load button at the bottom of the settings page. Use the file
browser to select the downloaded firmware.
4. Click the ‘Update Firmware’ switch to install the firmware on the amplifier. Do not interrupt this
process or the amplifier will become unusable. If the amplifier was not already in update mode,
the software will ask you to restart the amplifier while pressing the shutdown button.
17.4 Overview of User Interface Controls
Enable Switch - Enables and disables the amplifier output.
•Enabling the amplifier clears all previous overload
conditions.
Phase Tracking Switch - Enables and disables phase tracking.
•When enabled, the output frequency will be adjusted until
the measured phase equals the phase set point.
•When enabled, the output frequency cannot be manually changed.
•When the maximum frequency is encountered, the frequency will jump to the minimum, and
vice-versa.

PDUS210 V5 Manual 20 Modified 17/12/2022
Current Tracking Switch - Enables and disables current tracking.
•The output voltage will be adjusted until the measured current equals the current setpoint.
•When enabled, the output voltage cannot be manually changed.
•Recommended when tracking a series resonance.
•Will disable power tracking
•The voltage will not be adjusted until the phase tracking is locked, i.e. there is less than 10
degrees difference between the measured phase and the phase set point.
Power Tracking Switch - Enables and disables power tracking.
•The output voltage will be adjusted until the measured load power equals the power set point.
•When enabled, the output voltage cannot be manually changed.
•Will disable current tracking
•The voltage will not be adjusted until the phase tracking is locked, i.e. there is less than 10
degrees difference between the measured phase and the phase set point.
Remote Amplitude Switch - Enables and disables the front panel amplitude control.
•When enabled, the remote dial will change the output voltage from zero to the maximum
amplitude.
•If current tracking is enabled, the dial will change the current set point from zero to the
maximum output current.
•If power tracking is enabled, the dial will change the power set point from zero to the
maximum load power.
Max Power - The maximum power that can be supplied to the
load, in Watts.
•If this maximum value is exceeded, an overload will be
triggered and the amplifier output will be disabled.
Max Voltage - The output voltage limit, in Volts RMS.
•Limits voltage when power or current tracking is enabled
Max Current - The maximum current that can be supplied to the
load, in Amps RMS.
•Limits current when power or current tracking is enabled
Transformer Turns - The transformer turns for the FLEX version.
Voltage - Sets the output voltage, in Volts RMS.
•Cannot be changed if power or current tracking is enabled