IMKO TRIME-PICO 32, Руководство пользователя

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Manual TRIME_PICO64-32 Version 2_0 2017-05-30
Page 16
5 Remote Power Supply to TRIME-PICO
The operation of TRIME sensors may cause problems when power has to be supplied via long cables. There are
limitations
to the maximum cable length depending on the cable diameter.
When power is supplied over long distance the maximum cable length depends on the cable cross section A ,
the supply voltage V
s
and the number n of the sensors measuring simultaneously. Device-specific data also be
applied to the formula:
Power consumption during measurements: I
norm
= 100mA @ 12V/DC
Power consumption at min. voltage: I
max
= 175mA @ 7V/DC
Supply voltage: V
s
= 12V
Minimum sensor voltage at circuit end: V
min
= 7V
Wire cross section: A = 0,34mm²
Specific electrical resistance of copper:

= 0.0178
Ω
x mm² / m
Number of sensors: n = 1…
The maximum possible circuit length I
max
can then be calculated in the following manner:
max
min
max
2
) (
I n
V V A
l
s
  
 


Please see the following the following example:
In the IMP232 environmental measurement system a bus cable with a wire cross section of A = 0.34 mm
2
is
normally used. We further assume that the power supply voltage is V
s
=12 V and only one sensor is designated
to measure. Thus n = 1.
m
A
m
mm
V V mm
l 270
175 . 0 1 0356 . 0
) 7 12 ( 34 . 0
2
2
max

  
 

In the above calculation, no tolerance is included; for security reasons the calculated cable length should be
reduced by 10% to obtain a realistic value. In order to increase the maximum possible cable length several
solutions are feasible.
1. Using cables with larger conductor diameters
By using 6-core conductor cables instead of 4-core, the cable length can be doubled as two extra
cores can be used for power supply. Cables with conductors of larger diameters will further in-
crease the maximum cable length possible.
2. Increasing the power supply voltage
Power supply voltage can be increased up to 17V, thereby raising the maximum length from 270m
to 540m in the example calculation above.
3. Installation of buffer batteries in the distributor
Additional storage batteries close to the TRIME sensors, e.g. in the distributor, allow cable lengths
up to 1km and enable simultaneous measurement of several sensors. However, this method re-
quires an additional charging circuit for the buffer storage battery.
4. Installation of a voltage regulator at the distributor
Voltage loss in the cable can be reduced with a 30V power supply and an installation of a voltage
regulator directly in front of the TRIME sensor, thus allowing circuit lengths of up to 1km.
Which solution is best suited mainly depends on the nature of the power supply of the measurement system:
Battery supply : solution 1 and possibly solution 3 should be considered, the latter being relatively ex-
pensive.
Mains supply : solutions 1 and 2 could be combined, or, more expensive, solutions 2 or 4 could be cho-
sen.