Larson Davis HVM200, Reference Manual

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HVM200 Reference Manual C-3
Running RMS
Acceleration
EXPONENTIAL

Time constant of the measurement.
An averaging time of SLOW is equivalent to a time constant of 1 second.
Vibration Dose
Value
The VDV integration time is from Run to Reset; the display is updated once per second. The VDV is
not calculated for units of dB or g.
For whole body vibration mode:
VDV
sum
= max(VDV
x
+ VDV
y
+ VDV
z
)
Maximum Transient
Vibration Value
Amax = maximum reading of all Arms readings from Run to Reset.
The display is updated at the end of each Averaging time period.
Minimum Transient
Vibration Value
Amin = minimum reading of all Arms readings from Run to Reset.
The display is updated at the end of each Averaging time period.
Long Term
Maximum Peak
Amp = peak level of the instantaneous weighted acceleration, a
w
(t); measured over the entire
measurement period, from Run to Reset.
The displayed Amp value is updated once per second.
Short Term
Maximum Peak
Peak = peak level of the instantaneous weighted acceleration, a
w
(t); measured during one
Averaging time period.
The peak measurement period is controlled by the Averaging time setting; a new Peak value is
calculated and displayed at the end of each Averaging time period.
Summed
Instantaneous
Acceleration
a
w

(t) = instantaneous, summed acceleration
a
wx
(t), a
wy
(t), a
wz
(t) = X, Y, and Z axis instantaneous acceleration
K
x,
K
y,
K
z
= X, Y, and Z axis Sum Factors
The HVM200 uses the formula above to calculate the instantaneous,
summed acceleration, a
w

(t) . This value is then used to calculate a sum quantity for the
A
rms
,A
min
, A
max
, A
mp
, A
eq
, Peak, VDV, and PE.
K factors affect only sum value and not individual axis data.
Term Equation Description
Arms
1

---
a
w
2
t  
t t
0

------
 
 
exp t d

t
0

 
 
 
 
=
-
-
VDV a
w
4
t   t d
0
T

 
 
 
 
1
4
---
=
 
 
K a t K a t K a t
[
( )] ( )
[
( )]
x wx y wy z wz
2
2
2