in the drawings reference numeral 30 is alternatively related to the counter or controller . the physical arrangement of counter and controller could be at the same positions although their functions are different . fig1 shows a probe 18 according to the present invention while fig2 is a schematic illustration of a display and analyzer unit 10 for intra - cranial pressure measurement . a connecting cable 12 is connected to this unit 10 and , via a plug connector 14 which serves as coupler , to a catheter 16 . a probe head 20 is disposed on the distal end of the catheter 16 . the probe head 20 is inserted via an opening 24 into a patient &# 39 ; s skull 22 . the probe head 20 is located here between the dura mater and the cranial bones for measuring the epidural pressure . the probe 18 comprises a piezo crystal as pressure transducer , together with a bridge circuit , in a manner known per se . the bridge circuit is supplied with power via leads extending within the catheter 16 , with the unit 10 serving as energy source . a window 26 is formed in the connector 14 to permit an unobstructed view of a light - emitting diode 28 inside the connector 14 . fig3 is a schematic block diagram illustrating components inside the part 14 b of the connector 14 . a counter / controller means 30 , which cooperates with the light - emitting diode 28 and a switch 32 , is connected to the input side of the bridge circuit . the counter / controller means 30 is connected to the energy source of the bridge circuit via line 34 and via line 36 . alternatively a controller means can be used instead of the counter means . a voltage supplied by the energy source serves to operate a microprocessor 38 that cooperates with a memory 40 . the microprocessor 38 and the memory 40 are parts of the counter means 30 disposed inside the part 14 b of the connector 14 . the counter / controller means 30 comprises moreover data lines 42 and 44 connected to a data input 46 and a data output 48 . a predetermined number is input into the counter / controller means 30 via the data lines , and when this number is reached the switch 32 is actuated . the predetermined number is set by means of a computer . the measuring signals of the bridge circuit are transmitted via the lines 50 and 52 to the unit 10 . prior to the start of operation of the probe 18 , a predetermined number is input via the data lines 42 and 44 into the counter / controller means 30 , for instance twenty operational applications . furthermore , a period is specified via the data lines 42 and 44 , from which onwards a respective counting operation is to be performed . for example , when a voltage is applied to the lines 34 and 36 for at least half an hour , a counting operation is triggered . the counter / controller means 30 hence counts the number of operational applications , i . e . the pressure measurements , of the probe 18 . an operational application is then defined in such a way that a voltage must be applied to the lines 34 and 36 for at least half an hour . when the voltage has been applied for more than half an hour a counting operation is triggered . the counting operation then decrements from the specified number one unit at a time , so that the number of remaining operational applications is stored in the memory 40 . furthermore , the total number of operational applications is detected , which means that after each operational application the number is incremented by one and then separately stored in the memory 40 . the number of operational applications still remaining up to actuation of the switch 32 is indicated by a string of flashing signals via the light - emitting diode 28 . the switch 32 is illustrated in fig3 in a state in which the probe has not yet reached the predetermined number of operational applications . as soon as the specified number of operating applications is reached the switch 32 is closed to short the lines 34 and 36 . with this switching the bridge circuit is rendered inoperative and the probe 18 can no longer be used for tonometric applications . the user must then return the probe 18 to the manufacturer for calibration . after calibration , the manufacturer sets anew the specified number via the setting means 42 and 44 , so that the switch 32 will be opened again and the probe 18 is switched again into its state ready for operation . the counter / controller means 30 moreover comprises a data input 46 and a data output 48 via which the contents of the memory 40 can be read , which means that the manufacturer can establish how often the probe 18 has been in operation altogether and how often calibration has been performed . apart therefrom , additional data is stored in the memory 40 , specifically the customer number , the serial number , the data of delivery , the name of the person calibrating the probe 18 and the data of calibration , the date of last calibration of the probe , and similar information . the predetermined number of the counter / controller means 30 may be set and the operation of the probe 18 resumed via the data lines 42 and 44 and the data input 46 and the data output 48 , with the switch 32 then resuming its open position illustrated in fig3 . a series resistor 54 is inserted in line 34 — plus — so that the monitor of the display and analyzer unit 10 will not be affected . the probe 18 is made of a temperature - resistant and biologically compatible material and is adapted for complete autoclaving , together with the catheter 16 . the invention ensures in a simple manner that an electric counter / controller means 30 with small dimensions can be realized in the probe 18 , via which the predetermined number of operational applications is indicated . the switch 32 serves to prevent the probe 18 from being operative beyond the specified number of operating applications .
a probe for physiological pressure measurement in a human or animal body comprises a probe head , a line such as a catheter , and a pressure transducer , particularly an electric transducer , in the probe head . for measuring pressure , the probe head with the pressure transducer is disposed at a measuring site for pressure measurement , with the probe head being adapted for connection to an analyzer and display unit via the line . a counter or controller means is provided for recording a number of operational applications of the probe .