PTB 420 Auto
Tablet Testing Instrument with Integrated Balance and Feeder

The fully automated 4 in 1 tablet testing instrument PTB 420 Auto is a dual test mode instrument to determine the weight, diameter, thickness and hardness of tablets. The instrument is made in strict compliance with the EP <2.9.8> and USP <1217> Pharmacopoeia.

PTB 420 Auto features an integrated Sartorius analytical balance module to determine individual sample weights and a tablet feeder for up to 25 samples. Prior to testing the hardness of the tablet the PTB 420 can measure sample thickness (or height) and diameter (or length). The thickness is detected automatically by an optical system. The samples are automatically positioned by means of the patented movable alignment jaws. The behaviour of the jaw’s movement is adjustable to accommodate many different shapes of tablets and oblongs. The instrument can be set to either linear force or linear speed increase mode for the tablet hardness test. PTB 420 Auto offers two modes for the weight measurement: either weigh each sample individually, before placing them into the tablet magazine or weigh all samples together and calculate the average weight.

PTB 420 Auto features a large, back-lit color LCD. Menu navigation is done by use of a click wheel similar to the ones used in many car navigation systems. This allows the user to rapidly scroll through the menus to make his selections. Quickly create methods by entering the nominal test information for thickness, diameter, hardness and weight via the alpha-numerical keyboard and select the unit to measure (mm/in, Kp/N/Sc). It is also possible to use the quick test functionality to work without creating a method first and without entering any nominal values. When creating a method, it is also possible to disable certain measurements, for example to only test the hardness of a tablet. The angle of the operation panel can be adjusted freely to guarantee optimal visibility, whether the user is sitting in front of the instrument or operating it from a standing position.

To perform a test with PTB 420 Auto, insert the samples into the tablet feeder. The samples will be weighed and dropped one by one into the unique sample positioning station for automated correct alignment inside the combined thickness, diameter and hardness test station.

A class 1 laser beam is used for the touch free measurement of the sample thickness. The beam is used to illuminate a CCD-sensor on the other side of the measurement area. The sample is scanned by the laser beam while simultaneously being moved in front of the CCD-sensor by the moving sample dish. The height of the sample can be determined form the sample’s shadow on the CCD-sensor. Thereafter the sample is automatically moved towards the force jaw to measure the diameter and finally the hardness by breaking it.

Once the test is finished and the sample is broken, the sample dish moves backwards to drop the sample fragments into the removable waste container.

The results are immediately displayed and may be printed on a connected printer. The print-out includes each individual result as well as product information, date, time, user, instrument serial number and statistics.

The Feeder and Balance Module

PTB 420 includes a feeder for up to 25 samples and features an integrated Sartorius analytical balance. For tests with more than 25 samples, the instrument prompts the user to refill the feeder once the first 25 samples have been tested.

Before the samples are dropped into the combined thickness, diameter and hardness test station of the PTB 420 Auto, they are transported onto a balance dish integrated into the feeder. There the individual weight of each sample is determined. The feeder can be removed easily for cleaning purposed.

The feeder and testing station are covered by a transparent hood. This can be flipped back to easily fill the feeder. It features a detection system to ensure the instrument only runs when the hood is closed.

A Note on Calibration

The current USP Pharmacopeia requires the force sensor of a tablet hardness testing instrument to be calibrated periodically over the complete measuring range (or the range used for measuring samples) with a precision of 1N. All Pharma Test tablet hardness testing instrument can be statically calibrated over the complete measuring range by the use of different tracebale counterweights. All instruments support the checking of at least three different points during calibration to prove the linearity of the force sensor. Furthermore, Pharma Test offers the PT-MT magnetic tablets to calibrate the breakpoint detection of the whole tablet hardness testing instrument (force sensor and mechanics of the instrument). All Pharma Test tablet hardness testing instruments are fully compliant to the requirements of the current USP Pharmacopeia.


  • Tablet hardness testing in full compliance to USP <1217> and EP <2.9.8> Pharmacopeia
  • 4 results of the same sample: thickness, diameter, hardness and weight (via integrated Sartorius analytical balance)
  • Dual force mode instrument with linear speed increase and linear force increase modes
  • Stepless adjustment of the linear force or speed increase rate
  • Document all results on external printer
  • Multiple point validation procedure for all measurement stations built-in
  • Programmable print-out of force increase curve
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