PTB 420
Automated Hardness Test Instrument with Balance Connection

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

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 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. Furthermore, PTB 420 allows the connection of a Mettler-Toledo or Sartorius analytical balance to measure the weight of the samples as well. PTB 420 offer 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 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, either insert the samples into the tablet magazine or drop the individual samples 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.

Optional Accessories

The optional tablet transport magazine holds 10 samples, with a maximal diameter of 22mm and a maximum width of 30mm. The magazine is connected to the PTB 420 instrument by means of a magnetic coupling which is connected to the drive inside the PTB 420. The transport belt moves forward to drop one sample directly into the alignment jaws in the testing station of PTB 420. Once the test has finished and the broken sample is released into the waste container, the next sample is supplied automatically. The magazine can be refilled at any time to allow the testing of larger batches in one test run. As the tablet magazine can easily be removed from the PTB 420, it may be used to collect samples directly at a tablet press. In this case it is possible to use several magazines, one for each tablet press, for example.

The PTB 420 features a RS232 interface to connect a Mettler-Toledo or Sartorius analytical balance of 0.1mg accuracy. This way it is possible to test either the individual weight or average weight of all samples prior to the test of the physical parameters of thickness, diameter and hardness. The samples are placed manually from the balance either directly into the testing station of PTB 420 or into the tablet magazine.

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.


  • Fully USP <1217> and EP <2.9.8> compliant
  • 4 results of the same sample: thickness, diameter, hardness and weight (via connected external balance)
  • Dual force mode instrument with linear speed increase and linear force increase modes
  • Document all results on external USB printer (PCL5 capable)
  • Multiple point validation procedure for all measurement stations built-in
  • Programmable print-out of force increase curve
World Map Europe Asia North America Africa South America Australia