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Source Measure Unit User Manual


Source Measure Unit

  • Affordable and Accurate
  • Five Current Ranges
  • Dual Channels

£1300 With Free Shipping

1. Overview


The Ossila Source Measure Unit (SMU) incorporates two voltage sources for measuring current and two voltage meters for measuring voltage. With it, you can measure a wide range of research devices including photovoltaics, LEDs and OLEDs, transistors, and more.

The ability to control instruments is a key skill for experimental scientists and engineers. We have designed the SMU so that no matter what your skill level is, you can access affordable, precise instrumentation.

Source measure unit

1.1 Features

  • Dual Source Measure (SMU) channels
  • Dual Voltmeter (Vsense) channels
  • ±10 V source
  • Up to ±200 mA source/sink current per channel
  • Five software controlled current ranges (10 nA – 200 mA)
  • Shutter control or trigger input
  • Serial and I2C extension
  • PC software front panel
  • USB & network control
  • Simple text-based interface

2. EU Declaration of Conformity (DoC)


Please refer to the full PDF or print user manual for the EU Declaration of Conformity (DoC).

3. Safety


3.1 Warning

  • Do NOT connect external voltage sources to either SMU channel.
  • The absolute maximum input voltage for the Vsense channels is ±12 V. Do NOT apply input while not powered.

3.2 Use of Equipment

The Ossila Source Measure Unit is designed to be used as instructed. It is intended for use under the following conditions:

  • Indoors in a laboratory environment (pollution degree 2).
  • Altitudes up to 2000 m.
  • Temperatures of 5°C to 40°C; maximum relative humidity of 80% up to 31°C.

The unit is supplied with a 24 VDC power adapter with a power cord for the country of purchase, in accordance with European Commission regulations and British Standards. Use of any other electrical power cables, adaptors, or transformers is not recommended.

3.3 Hazard Icons

The symbols shown in Table 3.1 can be found at points throughout the manual. Note each warning before attempting any associated operations.

Table 3.1 Hazard warning labels used in this manual.

Symbol Associated Hazard
Electrical shock warning symbol Electrical shock

3.4 General Hazards

Before installing or operating the Ossila Source Measure Unit there are several health and safety precautions which must be followed and executed to ensure safe installation and operation.

3.5 Power Cord Safety

Electrical shock warning symbol

Emergency power disconnect options: use the power cord as a disconnecting method and remove from wall. To facilitate disconnect, make sure the power outlet for this cord is readily accessible to the operator.

3.6 Servicing

If servicing is required, please return the unit to Ossila Ltd. The warranty will be invalidated if:

  • Modification or service has taken place by anyone other than an Ossila engineer.
  • The unit has been subjected to chemical damage through improper use.
  • The unit has been operated outside the usage parameters stated in the user documentation associated with the unit.
  • The unit has been rendered inoperable through accident, misuse, contamination, improper maintenance, modification, or other external causes.

3.7 Health and Safety - Servicing

Electrical shock warning symbol

Servicing should only be performed by an Ossila engineer. Any modification or alteration may damage the equipment, cause injury, or death. It will also void your equipment’s warranty.

4. Requirements


The Ossila SMU is compatible with our Front Panel software which is included with the system. It allows for simple operation of the SMU and precision voltmeter channels. Table 4.1 details the minimum computer specifications for the Ossila Front Panel software.

Table 4.1 Ossila Front Panel requirements

Operating Systems Windows 10 or 11 (32-bit or 64-bit)
CPU Dual Core 2 GHz
RAM 2 GB
Available Hard Space 128 MB
Connectivity

USB 2.0

Ethernet

5. Unpacking


5.1 Packing List

The standard items included with the Ossila Source Measure Unit are:

  • The Ossila Source Measure Unit.
  • 24 VDC power adapter.
  • USB-B cable.
  • USB memory stick pre-loaded with the user manual, software installer, QC data, and USB drivers.

5.2 Damage Inspection

Examine the components for evidence of shipping damage. If damage has occurred, please contact Ossila directly for further action. The shipping packaging will come with a shock indicator to show if there has been any mishandling of the package during transportation.

6. Specifications


The Ossila Source Measure Unit contains four channels: two source measure units (SMUs) and two precision voltmeters. There is also a general-purpose shutter/trigger to allow other instruments to be controlled or control the unit.

6.1 Specification Conditions

The specifications and information in this document are for the Ossila Source Measure Unit. All units meet these standard specifications when dispatched to the end-user.

The accuracy of both source and measurement of the unit are specified under the following conditions:

  • Ambient temperature of 23°C ± 5°C, < 60% relative humidity.
  • After a 30-minute warm-up period.
  • Default measurement speed (OSR 5) unless specified.
  • No filter.

6.2 Source Measure Units (SMU 1 and SMU 2)

The source measure units output a voltage and then measure both the voltage and current. The output voltage is always measured at the output of the BNC (rather than assuming it is at the set voltage) in case of any load effects (for example short circuiting the output or low impedances causing a small drop in voltage). Each source measure unit has manually selectable ranges so that both high and low currents can be measured accurately.

6.2.1 Power Specifcations

The unit is specified for a maximum operation power as in Table 6.1. Figure 6.1 shows the fourquadrant safe operation zone of the unit.

Table 6.1 DC power specifcation

Power per SMU channel (continuous)
Four-quadrant Operation Source/sink 2 W (± 10 V at ± 200 mA)
Four-quadrant safe operation zone
Figure 6.1 The four-quadrant safe operation zone.

There is some allowance for being beyond these limits (± 10 V and ±200 mA). The unit has internal voltage and current limits set at ±10.5 V and ±225 mA. If a voltage or current greater than these values is measured on either SMU, the red error LED next to the SMU will turn on and the output voltage of the SMU will be set to 0 V. This is a measure to reduce the possibility of damaging the unit due to excessive voltages or currents. The voltage and current limits can be changed programmatically, but they should not be increased past the default values as this will increase the possibility of damaging the unit.

6.2.2 Measurement Speed

The Ossila Source Measure Unit utilises a high-speed, 24-bit no Latency ∆Σ™ ADC. It provides ten speed/ resolution combinations (6.9 Hz/200 nV RMS noise to 3.5 kHz/25 µV RMS noise) which can be selected, with no latency between conversion results. Additionally, a double-speed mode can be selected, enabling output rates up to 7 kHz with one cycle latency. These modes are linked to a single variable called OSR (Oversampling Rate) which is used to program the unit and take the measurement. Table 6.2 lists the various speed settings of the unit, with maximum measurement rates for both SMU and voltmeter channels.

Table 6.2 Measurement speed modes

OSR1 Index ADC Mode ADC (samples/data point) ADC2 RMS Noise SMU 1/23 (data points/Sec) Vsense 1/23 (data points/Sec)
0 x1 64 23 µV N/A N/A
1 x1 128 3.5 µV 525 785
2 x1 256 2 µV 276 414
3 x1 512 1.4 µV 142 213
4 x1 1024 1 µV 72 108
5 x1 2048 750 nV 36 55
6 x1 4096 510 nV 18 27
7 x1 8192 375 nV 9 12
8 x1 16384 250 nV 4.5 6
9 x1 32768 200 nV 2.2 3

1 OSR 10-19 will set the ADC in 2x mode with the same parameters of OSR 0-9, this will approximately double the unit’s measurement rate.

2 ADC noise increases by approximately √2 when OSR is decreased. Note that this is not the unit measurement noise levels.

3 Values based on 1000 data points per measurement.

6.2.3 Voltage Source and Measurement Specifications

Table 6.3 Voltage source and measurement specifications

Mode OSR Range Accuracy Precision Resolution
Sourcing N/A ± 10 V ± 10 mV 333 µV 1.7E-4
Measuring 1 to 4 ± 10 V ± 10 mV 100 µV 1.0E-4
5 to 9 ± 10 V ± 10 mV 50 µV 1.0E-5
Warning: Do not attach external voltage sources to either SMU channel as this may cause damage to the unit.

6.2.4 Current Measurement Specifiations

The current measurement of the Ossila Source Measure Unit is spread over 5 ranges. Each range has a different maximum current, accuracy, and resolution. As the range number increases, the maximum measurable current decreases, but the accuracy and resolution increase.

Table 6.4 Current measurement specifications

Range Max Current Accuracy1 Precision2 Resolution Burden
1 ±200 mA ±500 µA 10 µA 1 µA < 10mV
2 ±20 mA ±10 µA 1 µA 100 nA < 10mV
3 ±2 mA ±1 µA 100 nA 10 nA < 10mV
4 ±200 µA ±100 nA 10 nA 1 nA < 10mV
5 ±20 µA ±10 nA 1 nA 100 pA < 10mV

1Accuracy has been measured at the maximum current of that range.

2Precision has been measured at the highest OSR (9).

Warning: Do not apply currents to a SMU channel that are greater than the maximum current of the active range as this may cause damage to the unit.

6.3 Voltmeter (Vsense 1 and Vsense 2)

The Ossila Source Measure Unit has two additional voltage measurement channels marked as Vsense 1 and Vsense 2. They are designed to accurately detect small voltages while simultaneously having a wide dynamic range of ±10 V. Table 6.5 lists the specifications of these additional channels.

The Vsense modules share a ground plane with the SMU module of the same number (i.e., Vsense 1 shares a ground plane with SMU 1) and hence is not isolated.

Table 6.5 Voltmeter specifcations

OSR Range Accuracy Precision Resolution
1 to 4 1 to 5 ±10 mV 100 µV 1.0E-4
5 to 9 1 to 5 ±10 mV 50 µV 1.0E-5

6.4 Measurement Non-Linearity

The non-linearity in the measurement of the Ossila Source Measure Unit is kept well below the measurement accuracy of every range. Such non-linearity is common due to different amplification stages and analogue digital conversion processes.

6.5 Shutter/Trigger

The Shutter/Trigger can be used either as an input or an output. It can be used to send a trigger signal to other instruments or configured to wait for a trigger from other instruments. The voltage level of the Shutter/Trigger is 5 volts and can source and sink up to 30 mA of current; higher currents may result in damage to the unit.

6.6 Physical Specifications

Table 6.6 Ossila Source Measure Unit physical specifications

Channels

2 x source measure units (SMUs)

2 x voltmeters (Vsense)

1 x shutter/trigger

Channel Connectivity BNC
PC Connectivity

USB

Ethernet

Dimensions

Width: 125 mm

Height: 55 mm

Depth: 185 mm

Weight 0.55 kg
Power Supply 24 VDC

7. System Components


The Ossila Source Measure Unit is comprised of the Ossila Source Measure Unit (Figure 7.1) and the Ossila Front Panel Software (Figure 7.2).

Source measure unit schematic
Figure 7.1 The Ossila Source Measure Unit.
Ossila front panel software for source measure unit
Figure 7.2 The Ossila Front Panel software.

8. Installation


8.1 Power On

  1. Connect the power supply first to the mains outlet, and secondly to the unit. The red and green power LED (at the back of the unit) and the fan will both switch on.
  2. Leave for 30 minutes to warm up before performing any measurements.

8.2 USB Driver Installation

  1. Connect the unit to the computer using a USB cable.
  2. The USB drivers will be installed automatically. The unit will appear in the Device Manager under the Ports (COM & LPT) section as ‘USB Serial Device (COMX)’ as shown in Figure 8.1.
  3. Alternatively, the USB drivers can be installed by running the 32-bit or 64-bit installation file located on the USB memory stick provided with the unit.
Ossila Source Measure unit in the Device Manager
Figure 8.1 Ossila Source Measure unit in the Device Manager.

8.3 Connecting to a Network

The Ossila Source Measure Unit is designed to work with any network that supports DHCP. When the ethernet cable is plugged in, the unit will automatically detect and identify the network and register itself within a few seconds

For most networks, the unit will need no further work – simply plug in and wait for the DHCP to work, and it is ready to go. However, there are two situations where more steps are required:

(I) Networks Requiring Device Registration

Some large corporate networks (such as universities) have increased security levels and will only allow “known/registered” devices onto the network. If this is the case for your network, you will need to register the MAC address first. After this, the unit should be allowed on the network and will work as normal via DHCP (fully automatically from this point with no intervention). Many institutions have their own registration systems for computers and printers, and usually have online instructions on how to register a device. If needed, the MAC address of the unit can be obtained by connecting to it with the Front Panel software over USB.

(II) Static IP Networks

For a network without DHCP support, a static IP address must be set manually. This can be done by following these steps:

  1. Connect the Source Measure Unit to a PC using a USB cable.
  2. Disable the DHCP client of the device using the command “eth0 set dhcp false”.
  3. Set the IP address and other network parameters using the command “eth0 set network ip-address subnet-mask gateway-ip dns-ip”
  4. Save the changes to the board so that they are loaded when the device powers on using the command “eth0 save network”
  5. Disconnect the USB cable, then connect the Ethernet cable and the device should connect after a few seconds.

Alternatively, an external network router that supports DHCP can be used to connect to a static IP network.

8.4 Front Panel Software Installation

  1. Run the file ‘Ossila-Front-Panel-Installer-vX-X-X-X.exe’ on the USB memory stick provided.
  2. Follow the on-screen instructions to install the software.
The Ossila Front Panel software and Source Measure Unit USB drivers can also be downloaded from Software and Drivers page

9. Front Panel Software


  1. Start the Ossila Front Panel software and the window shown in Figure 7.2 will open.
  2. There are 6 main areas of the UI, which are detailed below:
    1. Connection controls
    2. Utility controls
    3. Front Panel
    4. Data Plot
    5. Logged Data
    6. IV Curve

9.1 Connection Controls

Connection controls before (top) and after (bottom) connecting to the Source Measure Unit
Figure 9.1 Connection controls before and after connecting to a Source Measure Unit.

(I) Connected SMUs

Select the connected Source Measure Unit that you want to use.

  • This box will be populated automatically with the connection address (COM port or IP address) of any Ossila Source Measure Units connected to the computer and network.
  • To rescan for connected units, click the blue refresh button next to the drop-down box.
  • This box is disabled whilst connected to a Source Measure Unit.

(II) Connect

Connects to the Source Measure Unit currently selected in the “Connected Systems” dropdown box. Once connected, all other elements of the software will be enabled.

  • This box is disabled whilst connected to a Source Measure Unit.

(III) Reset

Remotely resets the connected Source Measure Unit and reconnects to it.

  • This resets all settings to their default values.

(IV) Disconnect

Safely disconnects from the connected Source Measure Unit.

  • SMU 1, SMU 2, Vsense 1, and Vsense 2 will also be disabled.

9.2 Utility Controls

Utility controls in the software
Figure 9.2 Utility controls.

(I) Fan

Toggles the fan of the connected Source Measure Unit on and off.

(II) SMU Lights

Toggles whether the status LEDs of the SMU channels turn on when the channels are enabled.

(III) Shutter

Toggles the shutter output on and off.

  • The shutter outputs 5 VDC when switched on.

(IV) Log Data

Records the values of all channels in the logged data table, along with the current date and time.

  • Records 0.0 for channels that are switched off.

(V) Save Live Data

Toggles whether data will be continuously saved while a channel is switched on.

  • The data will be saved to the comma separated value (.csv) or text (.txt) file set in the “Save Data Path” field.

(VI) Save Data Path

Sets the directory and file name for saving live data.

  • If the selected file does not exist, it will be created.

9.3 Front Panel

The front panel tab showing each channel on the source measure unit
Figure 9.3 The Front Panel tab.

The Front Panel tab consists of a control panel for each of the channels on the Source Measure Unit: SMU 1, SMU 2, Vsense 1, and Vsense 2.

Control and output panel for the SMU channels
Figure 9.4 Control and output panel for the SMU channels.

Each SMU panel contains an on/off toggle button, voltage (left) and current (right) measurement displays, and the settings, which are detailed below.

(I) Set Voltage

Sets the output voltage of the SMU channel (maximum of ±10 V).

(II) Current Range

Sets the current range of the SMU channel.

  • This defines the upper limit and sensitivity of current measurements that can be be performed by the SMU channel. The values for each range are given in Table 6.4.

(III) Samples per Point

Sets the number of samples to be taken for each taken point (the OSR, see Section 6.2.2 for details).

  • A higher number of samples per point will improve the accuracy of a measurement but will increase the time taken for it to be performed.

(IV) Voltage Limit

Sets the maximum voltage that the SMU channel can source (default ±10.5 V).

  • If the measured voltage is above the voltage limit, the output voltage will be set to 0 V.

(V) Current Limit

Sets the maximum current that the SMU can measure.

  • If the measured current is above the set current limit, the range will automatically be switch to ±200 mA to prevent damage to the SMU.
  • If the SMU is already at ±200 mA, the output voltage will be set to 0 V.
Control and output panel for the Vsense channels
Figure 9.5 Control and output panel for the Vsense channels.

Each Vsense panel contains an on/off toggle button, the voltage measurement display, and the settings.

9.4 Data Plots

Data Plots tab
Figure 9.6 The Data Plots tab.

The Data Plots tab contains a pair of plots that display the last 300 live voltage and current readings from each of the channels on the Source Measure Unit. The upper plot displays voltage readings, and the lower plot displays current readings. Controls for channels and plotting can be found in the sidebar.

Plot control pannel for the SMU Plot control pannel for the Vsense
Figure 9.7 Control panels for the SMU and Vsense channels.

Each SMU panel contains an on/off toggle button, a legend line indicating the line colour for the device data, checkboxes for toggling whether SMU data are displayed in the plots, and controls for Set Voltage and Current Range as described in Section 9.3. Vsense panels contain an on/off toggle, a legend line, and a checkbox for toggling Vsense data display.

Below the device control panels are 3 plot control buttons. From left to right these are: pause/resume plotting, save data, clear plots.

Plot controls
Figure 9.8 Plot controls.

(I) Pause/Resume Plotting

Clicking the blue pause/resume button will pause or resume updating the plots with new data.

  • Plotting will automatically pause if all channels are switched off, and resume when a device is switched on.

(II) Save Data

Clicking the green save button will save the data currently in the plots. This opens a dialog box to navigate to the desired save directory and name the file.

  • The desired file type (comma separated value (.csv) or text (.txt) can be selected using the drop-down box to the right of the file name field.

(III) Clear Plots

Clicking the red clear button will remove all data from the plots.

(IV) Plot Display Controls

By default, the plots will automatically scale the axes of the plot to display all the data within it. The view can be controlled manually using the following mouse controls:

  • Left or middle click and drag – pan the axes.
  • Right click and drag – scale the axes.
  • Scroll wheel – scale the axes.

A specific axis can be controlled by using these controls on the axis labels. The axes can be reset by clicking the ‘A’ button in the bottom-left of the plot, as shown in Figure 9.9 (note, this button will only appear whilst the mouse cursor is over the plots).

Reset data plot axes
Figure 9.9 Button to reset the plot axes.

9.5 Logged Data

Logged data tab
Figure 9.10 The Logged Data tab

The Logged Data tab contains a table which stores the data recorded when the ‘Log Data’ button is clicked. There are two buttons to the left of the table.

(I) Saving Data

Data in the table can be saved by clicking the upper green button. This opens a dialog box to navigate to the desired save directory and name the file.

  • The desired file type (comma separated value (.csv) or text (.txt) can be selected using the drop-down box to the right of the file name field.

(II) Copying Data

Select the cell or cells of the data to be copied. Then either:

  • Right-click on the highlighted data and select ‘Copy’ from the menu.
  • Press CTRL+C on the keyboard.

(III) Deleting Data

The entire table can be cleared by clicking the lower red button.

Individual rows can be deleted by selecting at least one cell in each row for deletion, then either:

  • Right-click on the highlighted data and select ‘Delete Row’ from the menu.
  • Press the Delete key on the keyboard.

A confirmation box will appear before any data is deleted.

9.6 IV Curve

I-V Curve tab
Figure 9.11 The IV Curve tab.

The IV Curve tab contains controls for perform current-voltage (IV) measurements. The measurement can be customised with the following settings:

(I) Voltage Source

Select which SMU channel will be used for the measurement.

(II) Current Range

Sets the current range of the SMU channel.

  • This defines the upper limit and sensitivity of current measurements that can be be performed by the SMU channel. The values for each range are given in Table 6.4.

(III) Samples per Point

Sets the number of samples to be taken for each taken point (the OSR, see Section 6.2.2 for details).

  • A higher number of samples per point will improve the accuracy of a measurement but will increase the time taken for it to be performed.

(IV) Start Voltage

Set the voltage in volts at which to start the current-voltage measurement.

(V) End Voltage

Set the voltage in volts at which to end the current-voltage measurement.

(VI) Voltage Increment

Set the step size in volts for changing the voltage during current-voltage measurements.

(VII) Voltage Settle Time

Set the time in seconds between outputting a new voltage and measuring the current.

(VIII) Hysteresis I-V

Set whether to perform a reverse current-voltage measurement after the forward currentvoltage measurement has completed.

  • This reverses the set start and end voltages and uses the same voltage increment and settle time as the forward measurement

(IX) Secondary Voltage

Set the voltage in volts to be output by the SMU channel not selected in the Voltage Source field.

If the secondary voltage is set to 0 V, the secondary SMU channel will not be used.

(X) Saving Data

Clicking the green save button will save the data currently in the plot. This opens a dialog box to navigate to the desired save directory and name the file.

  • The desired file type (comma separated value (.csv) or text (.txt) can be selected using the drop-down box to the right of the file name field.

(XI) Clear Plot

Clicking the red clear button will remove all data from the plots.

(XII) Plot Display Controls

The plot has the same controls as detailed in Section 9.4.

10. Advanced Measurements


If you want to perform a measurement that is not covered by the Front Panel software, you can control the Source Measure Unit directly using a variety of programming languages. More information and the available commands can be found in the Programming Documentation

11. Troubleshooting


Most of the issues that may arise will be detailed here. However, if you encounter any issues that are not detailed here, then please contact Ossila.

Table 11.1 Troubleshooting guidlines for the Ossila Source Measure Unit.

Problem Possible Cause Action
No power The power supply may not be connected properly. Ensure the system is firmly plugged into the power supply, and that the plug is connected to both the adaptor and a working power socket.
The power supply adaptor has a fault. Contact Ossila for a replacement power supply adaptor.
Software does not start The wrong version of Windows is installed on the computer. Install the software on a computer with Windows 10 or newer.
The software has not installed properly. Try reinstalling the software.
Cannot connect to the system via USB The USB cable may not be connected properly. Ensure the USB cable is firmly plugged in at both ends.
The USB cable may not be connected to a working USB port. Try connecting the unit to a different USB port on the computer.
The USB cable is defective. Use a different USB-B cable, and contact Ossila if necessary.
The USB drivers may not be installed or may not have installed properly. Try installing or reinstalling the drivers, they can be downloaded from the address given in the Software Installation section.
Cannot connect to the system via network The MAC address of the unit is not registered with the internal network. Register the system on the network using the MAC address obtained via a USB connection (Section 8.3: Connecting to a Network).
The Ethernet cable may not be connected properly. Ensure the Ethernet cable is firmly plugged in at both ends.
The Ethernet cable is defective. Try using a different Ethernet cable.

Compatible Substrates

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