Aim-TTi SMU4201 Road Test | Final Review

Table of contents

RoadTest: Sign Up to Review the Aim-TTi Source Measure Unit SMU4201

Author: Attila Tőkés

Creation date: 10 Aug 2023

Evaluation Type: Test Equipment

Did you receive all parts the manufacturer stated would be included in the package?: True

What other parts do you consider comparable to this product?: R&S NGU401, Keysight B2901BL, Keithley 2450, GW Instek GSM-20H10

What were the biggest problems encountered?: The firmware upgrade process, including the version numbering, is a bit confusing.

Detailed Review:

Source Measure Units (SMU-s) are some quite interesting lab instruments. Because of their price, they are not that common, but in exchange they offer a high precision Multimeter, Power Supply and Electronic Load in the same instrument.

The Aim-TTI SMU4201 is recently released source measure unit, with 4 quadrant source, sink and measure capabilities. It has a 0.015% basic accuracy with 6½ digit resolution, and it can provide a voltage at up to ±210V, and current up to ±3.15A.

In this road test I will try to give an overview on the build quality, user interface, and most importantly, the performance of this instrument.

Previous blog posts in this road test:

 Aim-TTi SMU4201 Road Test | Unboxing, First Look and User Interface 

 Aim-TTi SMU4201 Road Test | Power Supply and Load Experiments 

 Aim-TTi SMU4201 Road Test | Automated Experiments - Characterizing a Zener Diode 

 Aim-TTi SMU4201 Road Test | Automated Experiments - Li-Battery and MOSFET Characterization 

1. Form Factor & Build Quality

In terms of form factor, the SMU4201 is fairly compact, Aim-TTi claims that is "smallest bench top smu on the market". Its dimensions are 250mm (W) x 97mm (H) x 295mm (D) with handles and bumpers, and 213.5mm (W) (½ rack) x 86.5mm (H) (2U) x 269mm (D) with the accessories removed (for rack mounting).

The instrument comes with a handle + stand combo fit to it. This can be used to set the device in 4 positions, 3 of which are standing positions, and the 4th is for carrying. Compared to leg style stands, the combined handle + stand is maybe a bit bulky, but I think it also allows more comfortable settings. I tend to use it the uppermost setting, which gives o good viewing angle with the instrument sitting on the bench.

The various connectors and interfaces are available on the front and back panels if the device. The front panel of the SMU comes with a touch screen (about ~11 cm / 4.3 inch in diameter), a rotary knob, a couple buttons, 4 + 1 terminal posts and an USB port:

The back panel comes with screw-less terminals, power socket, digital I/O interface and LAN and USB ports.

The build quality of the instrument fields pretty good, as expected for the price. The only complain I have is that the on the front the 5 terminal posts and the casing on the front are quite misaligned.

More details and photos about the instrument and packaging can be found in my Aim-TTi SMU4201 Road Test | Unboxing, First Look and User Interface blog post.

2. User Interface

The user interface of the Aim-TTi SMU4201 consists of a 4.3 inch touch screen, a rotary knob and a couple of buttons.

With a few exceptions, most of the actions are controllable both with the touch screen or the rotary knob.

The main screen shows us the main settings, and as well the primary and secondary measurements:

The instrument's settings are accessible from the menu system in which we can enter by pressing the Config button.

There is an Easy Setup menu that can be used to rapidly set the instrument into various Source, Sink and Measurement modes. More advanced options are available in the Manual Setup mode, while from the rest of the menus we can access configuration and data store settings.

Overall the user interface is good and easy to use. In some places I observed minor bugs and weird behaviour, but those were not significantly affected the usability of the device.

More details overview of the menus and interfaces can be found in the Aim-TTi SMU4201 Road Test | Unboxing, First Look and User Interface blog post linked above.

3. Experiments

To test the instrument I performed several experiments, including manually executed and automated ones.

In the Aim-TTi SMU4201 Road Test | Power Supply and Load Experiments blog post, first I evaluated how the instrument performs when used as Power Supply connected to resistive, capacitive, and inductive loads. The experiments where performed on both for the SMU4201 and the Aim-TTi QPX750SP power supply I road tested before. The noise and ripple values for the resistive and capacitive loads were excellent, as expected for a precision lab power supply. The inductive load test showed some oscillations on both instruments, but that was more to do with the rough test load than the instruments.

Next, I checked the Electronic Load modes (Load Resistance, Load Current and Load Power) the instrument offers. For this as used the QPX750SP as a power supply, while the SMU4201 acted as a programmable load. Finally, I showed how to use the 4-Wire measurement mode to measure low resistances, such as zero-ohm link.

In the Aim-TTi SMU4201 Road Test | Automated Experiments - Characterizing a Zener Diode post, I started experimenting with the remote programming capabilities of the instrument. As the first use case I choose to characterize a Zener diode.

First, I briefly checked out the Test Bridge SMU software available for the instrument. This is a Windows only software, the allows controlling up to two Aim-TTi 4000 series SMU-s. The software worked relatively well, it has some interesting features, but otherwise it is not something extraordinary.

After this a went ahead to check out the SMU4000 Series Programming Manual which describe how to programmatically control the instrument over one of its remote interface. Of course I went with LAN LXI interface, and programmed it Python code implemented in Jupyter Lab notebooks. For the diode characterization I implemented an adaptive sweep algorithm that allows to plot an I/V curve with a high number of test points concentrated to the rapidly changing parts of the curve.

With the Aim-TTi SMU4201 Road Test | Automated Experiments - Li-Battery and MOSFET Characterization blog post I continued the road test with some Li-Battery characterization. This turned out to be a bit of a endurance testing of the SMU4201, as because of various issues (like bad connections, dodgy batteries and coding bugs) quite a number of charge and discharge cycles were executed.

In the end I got some usable data, showing how the measured capacity of a Li-Ion battery decreases as the discharge current is increased.

I also tried to do some MOSFET characterization, which is an use cases that is often described as needing two SMU-s to be done. 

In some cases however the one of the SMU-s could be replaced with a power supply, or even a micro-controller with a DAC. I tried with the QPX750SP, and managed to a Resistance vs. Gate voltage plot, as shown bellow:

My overall experience during the experiments was that SMU4201 is quite responsive, and no glitches or communication issues were observed. 

The only slowness I observed is when in Source Voltage modes the power is turned on with a load the results in the Constant Current mode being activated. This usually freezes the screen for about 2-3 seconds, after which the SMU works as expected.

4. Specifications & Competitors

Obviously, the Aim-TTi SMU4201 is not the only Source Measure Unit (SMU) available on the market, so naturally I wanted to see how the instrument compare to its main competitors.

In this comparison I included modern SMU-s with a touch screen interface and LAN / LXI connectivity. From the Aim-TTi I included both the SMU4201 and the lower voltage SMU4001 model, while from other manufacturers I included the model with the lowest price (which is usually a lower voltage model).

Bellow is a table comparing models from 5 manufacturers:

(*) - value applies only for certain settings
(**) - prices are current "street prices" on Farnell

As we can see the specification of the Aim-TTi SMU4201/4001 is quite on par with the competition, while a offering a good price.

5. Conclusions

During my road test the Aim-TTi SMU4201 performed exceptionally well. I specially liked the relatively small form factor, the quick setup functions and the responsiveness of the LAN interface.

The only slightly bothering things were the firmware upgrade process and some UI bugs.

The ~5000 USD price seems for the SMU4201, and especially the ~3850 USD price for the SMU4001 seems to be a very good deal.

In conclusion, I think the Aim-TTi SMU4201 is an instrument with pretty impressive specs for a reasonable price (ok  maybe not for hobbyists).

Hope you enjoyed this Road Test!