CALAMP WIRELESS NETWORKS INC. MCUC5 Manual Do Utilizador

 

Current value of supply voltage. This is a 4 digit
signed value in volts, e.g. a value of 13.3 indi-
cates 13.3 VDC. This value should remain
within the limits of 10-16 VDC.

 

Received Signal Strength Indicator (RSSI) for
the last data reception prior to this transmission.
This is the strength of the signal from the master
station as received by this remote. This is a 4
digit signed value in dBm, for example a value
of -090 indicates a signal strength of   -90 dBm.

 

The remote RSSI indicates the received signal
strength for the last data transmission received
before transmission of the online diagnostics
report.

 

RSSI for the current transmission. This is the
strength of the last data reception from the re-
mote station as received by the master. Condi-
tions described in the Remote RSSI section ap-
ply.

 

Typical values of RSSI will be in the range of
-110 dBm to -60 dBm, with higher values (i.e.
less negative values) indicating a stronger sig-
nal.

 

Reliability of data reception depends largely on
signal strength. Good design practice calls for a
minimum 30 dB “fade margin”, based on a
threshold reception level of -107 dBm (1 uV) at
speed of 9600 b/s. Experience indicates that this
will give about 99.5% reliability.

 

Some representative performance values for
9600 b/s operation are given below. These val-
ues assume that the units are correctly aligned
and installed in a quiet location. Environments
with high electrical or RF noise levels will re-
quire an increase in the numbers shown to
achieve a given level of reliability.

 

-100 dBm. Approximately 50% reliability.

Fading may cause frequent data loss.

 

-90 dBm. Approximately 90% reliability. Fad-

ing will cause occasional data loss.

 

-80 dBm. Approximately 99% reliability. Rea-

sonable tolerance to most fading.

 

-70 dBm. Approximately 99.9% reliability with

high tolerance to fading.

 

If RSSI values drops seasonally, the most likely
cause is tree foliage, which can interfere with
radio transmissions during the spring and sum-
mer.

 

Approximate measure of transmit power. This is
a 4 digit value in  watts rounded to the nearest
tenth.  Note that this is an approximate value
that should be used for trend monitoring
only. It does not compare in accuracy with val-
ues obtained by a standard wattmeter.

 

The values returned are approximate and should
not be regarded as an absolute indicator of per-
formance. For example, a unit that shows a for-
ward power of 4.5 watts may actually measure
at 5.0 watts on a lab quality wattmeter. For this
reason, these values should not be used to indi-
cate that a unit is out of spec or to compare one
unit to another.

 

 

Therefore the following conditions are worthy
of investigation.

1.  Forward power output drops or rises by

more than 10% from its established value.
Reflected power remains low.

This indicates that the transmitter may need
alignment or that a component may be in
need of replacement.

2.  Forward power output drops by more than

10% from its established value. Reflected
power shows an increase.