Bently Nevada 3300/50, Руководство по эксплуатации

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Tachometer Maintenance
112 I Events Per Revolution Adjustment (Cont)
Example 5:
In t h i s example, b o t h probes a r e
observing an eighteen tooth gear on the
same shaft with an eleven tooth gear.
The eleven tooth gear is driven from a
24 tooth gear. The Tachometer i s to
indicate the speed of the shaft on the
24 tooth gear. In this case, the Events
per Revolution (E/R) must be calculated:
E/R = (24 / 11) x 18 ; E / R = 39.2727
PROBE A
To set the Tachometer to the proper
E/R, the closest fraction must be found.
The maximum E/R numerator allowed is ' * \
255. The maximum denominator allowed a 4 room GEAR
is also 255. The closest fraction found
which is within these limits is E/R =
157/4. The E/R numerator is 157 and the denominator is 4. (157/4 = 39.25) Since 157/4 equals
39.25 and not 39.2727, a slight error will result. In this particular example, the error is 0.06 %, or 2
RPM at 3600 RPM.
I I TOOTH GEAR
EVENTS P E R R E V O L U T I O N
NUMERATOR
EVENTS PER REVOLUTION
DENOMINATOR
TACHOMETER I S TO
INDICATE THE SPEED
OF THIS SHAFT
83871-01 •
e0
TACHOMETER
' 1 5 7
WARN I NO
um w k .
4
PROSES
BOTH PROBES
OBSERVING l e TOOTH GEAR
IB TOOTH GEAR
Notes on Events per Revolution
TACHOMETER I N S P E C I A L
EVENTS P E R R E V O L U T I O N
ADJUST MODE
Depending on the operating speed, the Tachometer is limited to certain maximum values for the
Events per Revolution. The table below must be adhered to for +1- 1 RPM accuracy.
RPM Full Scale Range M a x i m u m Allowed Events per Revolution
100 RPM 2 5 5
200 RPM 2 5 5
500 RPM 2 5 5
1000 RPM 2 5 5
2000 RPM 2 5 5
5000 RPM 1 2 0
10,000 RPM 6 0
20,000 RPM 3 0
50,000 RPM 6
100,000 RPM 1
•
When operating at speeds below 100 RPM with one Event per Revolution, the update rate and Alert
•
speed up the update rate and the Alert response time.
20