Here we answer your questions about IBIS nanoindenters and associated technology.

1. Why does IBIS (and UMIS) use LVDT sensors?

LVDT sensors are “linear variable differential transformers” and are essentially inductance displacement sensors. They are inherently linear, and have sub-nanometre resolution. Their performance is very similar to the capacitance sensors used by other manufacturers with one very important exception. LVDT’s are very robust. A capacitive sensor consists of two, and sometimes three, parallel plates. Unfortunately, the plates have to be, by necessity, of very precise geometry, and be positioned very close together. It is common to make these plates from glass, and very common for the plates to break if the indenter shaft, which is connected to the centre or moving plate, is pushed or pulled unintentionally beyond the spacing (less than a mm) of the plates. By contrast, the LVDT sensors used in IBIS are made from stainless steel with a titanium shaft. The centre shaft passes right through the device and so the IBIS nanoindentation head can withstand significant abuse by untrained or inexperienced operators without damage. Experience over 20 years has shown that not one single repair to these sensors has been needed.

2. What's so good about a closed loop system?

In UMIS, and IBIS, the design of the head is quite different to competitor instruments. In our instruments, there is a separate, dedicated force sensor. The output from the force sensor is compared to the user set-point and the difference is fed back to the pzt actuator. This is a closed-loop system. in UMIS and IBIS, this happens in real-time in the electronics, and is not simulated digitally as in some competitor instruments that claim closed loop operation. The advantage is that the load is kept at the requested set point no matter what the indenter is doing – this is particularly important for creep and scratch testing. In standard nanoindentation tests, the closed loop system ensures that repeated tests are performed at exactly the same load increments in a precise and repeatable manner. In competitor systems, the situation is quite different. One popular instrument uses the current in the coil as a measure of the force applied to the indenter. The problem with this system is that the current in the coil is also used to deflect the indenter shaft support springs. The current that is used for this deflection has to be subtracted off in order to arrive at the residual current representing the penetration resistance of the sample. Issues such as resistive heating of the coil also affect the current draw. Such systems are typically calibrated by hanging weights on the indenter shaft and measuring the residual current. With UMIS and IBIS, the force sensor produces a signal which is linearly proportional to the indenter load 100%, there is nothing to subtract off. This closed loop system has been a feature of UMIS (and now IBIS) since 1989 and the special integrator loop in the circuitry has been designed to eliminate the possibility of deleterious overshoot that can occur in less well-designed systems.

3. What's the difference between a top-reference and a surface-reference nanoindenter?

The majority of nanoindentation instruments are top-reference, or frame-reference devices. This means that the depth sensor datum is the frame of the instrument. This has some advantages and some disadvantages. The main advantage is that the depth signal coming frmo the sample is due to movement of the indenter within the sample itself whereas in a surface-reference device, where the depth datum is the specimen surface, any movement of the surface (such as sinking in of the reference ring or ball) represents a moving reference point. Top references devices have more room around the indenter for ease of access to the indenter for changeover, are able to accommodate specimens of different height, and by necessity, are more robust in construction for better mechanical noise stability. Proponents of surface reference devices often neglect to state that their instruments cannot do scratch testing unless a separate head is fitted, often claim superior resistance to the effects of thermal drift - without realising that most of the effects of thermal drift are due to changes in dimension of the contact point, not the instrument or the indenter shaft, are not suitable for testing of soft materials or undertaking creep experiments. The surface ring or probe must make contacts with a reasonable force (to squash out any asperities in surface roughness so as to attain a good contact) and this leads to an undesirable uplift of the specimen surface in the vicinity of the indentation and creep into the specimen during the test. One must consider that with the 10 or so various nanoindentation instruments on the market, only one or two have been designed as surface reference devices.

4. How important is calibration?

Calibration is vital, and this is where UMIS and IBIS have another significant advantage over other instruments. UMIS was developed at the laboratory that is responsible for the dissemination of physical standards in Australia. The force and depth sensors with UMIS and IBIS are separately calibrated using an extremely short validation path to primary standards of mass and length. Competitor instruments typically use industrial standards that are somewhat removed from the primary standard by comparison. Worse, such instruments, with a combined force sensor/actuator, have difficulty in establishing the true force applied to the indenter independent of the support spring deflection and resistive heating. Deficiencies in these types of calibrations are often masked by the indenter area function determination and are not noticed by the user until a sample with mechanical properties different to that used for the area function is tested. With UMIS and IBIS, the force and depth sensors are independently calibrated and many years experience shows that these sensors will retain their calibration for over 15 years and longer.

5. What about customer service? Is there a local rep I can call upon for help?

In some cases, there is local representative for UMIS and IBIS instruments. Even though a competitor company may offer the services of a local representative, and provide some semblance of peace of mind, in reality, any enquiry of substance will be forwarded to head office and your question will be passed through several hands before being acted upon. With Fischer-Cripps Laboratories, our agents and customers deal direct - direct with the engineer, the programmer or the scientist. 95% of problems can be solved by email or direct network connection. Often problems occur when the user of the instrument is new and needs some advice.
Staff working on UMIS and IBIS have been with the program for many years. We have a personal commitment to our customers, many of whom have become good friends. You don't deal with a faceless multinational company, but real people who are interested in your problems and solutions.  With a small dedicated team, our business model is unusual compared to most instrument companies but we are justly proud of our products which we know will last for many years and provide quality, reliable data. Contrary to some belief, we are able to sell direct into the EU market at a competitive price.

6. Say I am interested, can you test a sample?

Generally yes. However, don't just send a sample without contacting us first. We will want to know if the sample is suitable for nanoindentation testing. Usually, a test is offered at no charge to demonstrate the capability of the instrument. However, if the sample is difficult, or a material that is not normally tested with this type of instrument, a charge for time spent may be appropriate  (refunded against any future purchase).

7. How important is experience?

It's vital. It's easy for an instrument company to publish specifications and have a product designed yesterday, but in reality, there's a whole lot of detail needed to get it right in nanoindentation. This attention to detail comes only at a cost - and that is, with time. The IBIS instrument builds upon the 20 year product history of UMIS so that it will work reliably and consistently. Every instrument is individually calibrated, checked, and verification tested against three standard specimens. The design eliminates issues that plague competitor instruments. We've recently seen some results taken with a fairly new-to-market competitor and unfortunately, while there is a lot of marvellous gloss, the unfortunate manufacturer, and their possible customer, have not appreciated the instrumental issues involved in working at the nm scale and their load-displacement curves are resplendent with subtle but significant errors only visible to an experienced eye. Unfortunately, these errors are easily masked by the indenter area function until the customer comes to test a specimen with different mechanical properties than that used for indenter calibration. With UMIS and IBIS, real time feedback, specially designed servo loop, low noise amplification, rigid frame, consistent robust and powerful software, and 20 years experience etc all add up to an instrument that works well.

8. The price you show is incredibly competitive, is this instrument high quality?

Yes. With IBIS, the aim has been to cut down on unnecessary frills, gadgets and custom made items and concentrate on the core capability of nanoindentation. We can offer this level of instrumentation at this price becuase the development costs have been recouped during the last 20 years of the product history. This instrument will provide results you can have confidence in. The three year warranty, traceable calibration, the experience in instrument design, the meticulous attention to detail, puts this instrument far ahead of its competitors. We offer real value for money, not a cut-down cheap product designed to attract your attention. IBIS is a quality instrument that represents what nanoindentation should be - reliable, accurate and affordable.