In this post we discuss in more detail and offer more data on the margin of error of volumetric measuring instruments with pistons.  Our special thanks go to Hirschmann and Hirschmann Laborgerate for providing this great information.

Volumetric measuring instruments with pistons

Error margins associated with volumetric measuring instruments with pistons (e.g. opus, solarus, ceramus, labopette) are indicated by the accuracy (A) and coefficient of variation (CV). A precondition in this respect is that a measurement be repeated several times.  Pertinent standard: EN ISO 8655.

1.1.  Accuracy (A)

Accuracy(A) is the deviation of mean value of all measurements from setpoint value

1.2.  Coefficient of variation (CV)

Coefficient of variation (CV) is the ratio of distribution of individual measurement values relative to each other when compared to the mean value. The smaller the CV, the closer the values are to each other. An approximate determination indicates that approx. 68 % of all measurement values lie within the CV and 95% of all measurement values within 2 * CV.

1.3.  Absolute errors

An approximate calculation of absolute margins of error |R| + 2 * CV is now possible for a confidence level of 95%.

1.4.  Example

IF we assume a setpoint volume 10 ml, A: +0.5 ml, CV: ± 0.3 ml, then:

The mean value is 10.5 ml.
Approx. 68% of all values lie between 10.2 and 10.8 ml. (1* CV)
Approx. 95% of all values lie between 9.9 and 11.1 ml. (2* CV)

1.5.  Comment

Where the values for A and CV are specified in %, it should be noted that the specifications always relate to the nominal volume of the instrument. This is of relevance where the test volume is less than the nominal volume of the instrument.

1.6.  Permissible margins of error for 50 ml piston burettes

Table 1

Glass volumetric measuring instruments

Absolute margins of error should not be exceeded in the case of glass volumetric measuring instruments (e.g. 10±0.02ml).

2.1.  Permissible margin of error for Cl. A 50 ml glass burettes

Table 2

Welcome to our inaugural blog post! As a part of our Know Your Laboratory Equipment series, in this post we go over the digital burette – what it is, what are some of its key features and how to select the right digital burette for your needs. This post concludes with a recommendation for the Hirschamnn Solarus digital burette.

What is a digital burette?

A digital burette, commonly known as bottletop burette, is a laboratory device used to dispense precise volume of a liquid reagent in titration experiments. Designed to replace the traditional glass burette, the digital burette uses a microprocessor and innovations in liquid handing to control dispensing and delivering improved performance, efficiency and safety.

Key features of the digital burette

• LCD screen to displayed volume dispensed
• User controls
• Electrical power
• Chemical resistance
• Light protection
• Recirculation system
• Computer interface for data logging
• Connection to external tubes and filters
• Factory and user-specific calibration
• Threaded connector to common bottles
• Sterilization of parts

Selecting the right digital burette

Like selecting any product, when looking for the right digital burette you need to consider price, accuracy, usability and reliability.

A quick disclosure: we work with many different manufacturers of laboratory products including Hirschmann, and it is our opinion that the Hirschmann Solarus is the best choice for laboratories in general and waste treatment plants and water treatment plants in particular. Here’s how Hirschmann digital burette stacks up to other popular digital burette manufacturers: Hirschmann, Brandtech, Brinkmann and Jencons.

Digital burette comparisons

Price: Hirschmann 20ml and 50ml have the same MSRP of $899, which is lower than BrandTech’s Titrette and substantially lower than Brinkmann (about $1,275) and Jencons’ Digitrate Pro (about $1,150). Hirschmann’s price includes PC interface functionality while BrandTech’s does not.

Accuracy: BrandTech is the only company that makes an explicit claim that compares the accuracy of the Titrette to the accuracy of class A glass burette.  Other manufacturers such as Hirschmann offer the more standard compliance to ISO 8655-3 with an absolute accuracy of 0.2 %.

Usability: In addition to including all of the features listed above, Hirschmann is the only model that uses a fully available solar panel to power its digital burette, which makes it the most environmentally-friendly digital burette. BrandTech, Jencon, and Brinkmann models use replaceable batteries. Hirschmann also has the largest LCD display for easy reading and soft-touch hand wheels.

Reliability: Each and every Hirschmann unit is individually tested for quality and accuracy which certifies to the conformity with the German “Eichordnung”. Hirschmann also backs its products with a 15 month manufacturer warranty.

Follow this link for more information on Hirschmann Solarus Digital Burette, and check back for other reviews and comparison of laboratory liquid handling products.

Thank you for coming to the Hirschmann Product Blog. This blog is about all things Hirschmann, including:

• Tips and tricks to using pipettes, digital burettes, bottletop dispensers and precision capillaries
• Frequently asked questions about our products
• Product announcements and promotions
• And much more

Please feel free to contact us with post suggestions, and check back soon!