With the ▲▼ keys the displayed value can be increased or decreased, until it
amounts to 10.00 m/s². To save the setting press OK and exit the menu. By adjusting
the transducer sensitivity the instrument has now been calibrated. Check the calibra-
tion in the measuring mode. A vibration acceleration of 10.00 m/s² at 159.2 Hz cor -
responds to a vibration speed of 10.00 mm/s s.
10. Sensor Check
The VM25 input is designed for use with a low power IEPE accelerometer. These
sensors are supplied by constant current, which produces a positive DC voltage po-
tential at the output. Due to this DC voltage an assessment can be made of the sen -
sor's operating condition. The VM25 detects three operational conditions:
< 0.1 V:
short circuit
0.1 – 11 V:
in working order
>11 V:
open input, e.g. broken cable
If a short circuit occurs or the input is open the instrument will display “SENSOR
ERROR” instead of the measurand.
11. Headphone Output
Some maintenance technicians possess experience in the acoustic assessment of me-
chanical vibration on machines. For this purpose the VM25 has a headphone con-
nection socket, which is also used for the USB connection. To connect a standard
headphone set with a 3.5 mm phone jack to the 8 pin socket, use the VM2x-HP
adapter cable which is included with the VM25 (Figure 42).
To use the headphone connection open the main menu by pressing F3 and select
“Headphone output”. Within this operation mode the volume can be adjusted using
keys ◄►(Figure 44). Press F3 to finish using the headphones.
32
Figure 41 Headphone cable VM2x-HP
