LS SERIES SERVICE MANUAL
ISSUE 4.0 EXTENSION MEASURING SYSTEM 1
5. EXTENSION MEASURING SYSTEM
5.1 Internal Extension Measurement
See diagram 04/1455 sheet 4 in section 17
The crosshead movement is measured by counting the pulses generated by a high-resolution
digital encoder which is directly driven by the motor shaft. The encoder produces 2 squarewave
signals that are 90 degrees out of phase and of 1:1 mark/space ratio. The phase of the two
encoder signals is important to ensure that the extension increases and decreases correctly. The
phase is selected by links on the Main PCB as shown below: -
The encoder pulses are connected to P2 on the Main PCB where they pass through the
relevant links and then are level shifted by TR1 and TR2. The pulses are then buffered by IC17
then fed to the microprocessor IC21 where they are counted by the internal up/down counter
and converted into an extension reading.
The microprocessor controls the crosshead speed by calculating the required rate of change of
crosshead movement then generating the required PWM signal.
5.2 External Analogue Extensometer
See diagram 09/1047 in section 16 and diagrams 04/1408 or 04/1463 in section 17
A single /E Series ANALOGUE External Extensometer can be connected to the 37 pin D
connector on the rear of the machine by using an adaptor cable, part number 09/1047.
One, two or three /E Series ANALOGUE External Extensometers can be connected
simultaneously to the machine by using an extensometer interface box, part number 01/3095.
The box is connected to the machine using a 37-way cable and each extensometer is
connected to a 25-way D connector on the extensometer interface box. The circuit diagram for
the interface box PCB (04/1461) is shown in section 17.
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