XT2640 Operating Manual
13 July 2016
Page 27 of 187
Recommendation:
In most cases both speed and torque will be measured, allowing an accurate computation of mechanical power to be made
available by the XT2640.
The best method for determining speed (and direction) is to use a shaft encoder with quadrature digital outputs. This
enables speed and direction to be obtained very accurately. Unless the motor or generator is known to have no mechanical
chatter when stopped or running at low revolution speeds, then the use of both the digital SPD and DIR inputs is
recommended as this will automatically correctly measure the mechanical speed when such chatter is present, otherwise
the indicated speed may be seriously affected by chatter if only a single digital signal for speed is used.
9.8.1
MECHANICAL
SPEED
AND
DIRECTION
INPUTS
If required, mechanical speed and direction can be input to the XT2640 using a DC analog voltage, or by using one (speed only) or
two (speed and direction) digital inputs.
9.8.1.1
DC
ANALOG
VOLTAGE
SPEED
If using a speed transducer with a DC voltage output then this output is connected to the SPD input BNC connector of the XT2640 MT
channel. The polarity of this signal implies the direction of rotation of the motor or generator. You will need to configure the SPD
input as ANALOG and set the scaling and offset settings accordingly for the specific transducer being used. The signal range is +/‐
12Vpk.
9.8.1.2
DIGITAL
SPEED
AND
(OPTIONALLY)
DIRECTION
If using a digital speed (optionally with direction) transducer such as a shaft encoder then the digital signals should be connected to
the SPD BNC connector and the DIR BNC connector as applicable. You will need to configure the number of pulses of the SPD signal
per revolution of the motor or generator, and the digital polarity of the DIR signal. The digital signals are CMOS/TTL compatible and
either rising or falling edge of the SPD signal can be configured to be used.
9.8.2
MECHANICAL
TORQUE
INPUTS
If required, mechanical torque can be input to the XT2640 using a DC analog voltage, or by using a digital pulse frequency input.
9.8.2.1
DC
ANALOG
VOLTAGE
TORQUE
If using a torque transducer with a DC voltage output then this output is connected to the TRQ input BNC connector of the XT2640
MT channel. You will need to configure the TRQ input as ANALOG and set the scaling and offset settings accordingly for the specific
transducer being used. The signal range is +/‐12Vpk.
9.8.2.2
DIGITAL
TORQUE
If using a digital torque transducer then the digital signal should be connected to the TRQ BNC connector. You will need to configure
the TRQ input as DIGITAL and set the scaling and offset settings accordingly for the specific transducer being used. The digital signal
is CMOS/TTL compatible.