Mantracourt Electronics Limited
DCell & DSC MantraCAN User Manual
59
Communications Cabling and Grounding Requirements
below).
Soldering Methods
Take care soldering cables to the pads. Use a temperature controlled soldering iron set to a maximum 330ºC, for no
longer than 2 seconds per pad. Excessive heat or increased soldering time may result in damage to the PCB.
NOTES:
1.
Solder with water-soluble flux should not be used (even low-residue), as this can leave a surface film which
attracts atmospheric moisture, degrading measurement performance.
2.
DCell units can be damaged by poor soldering, due to the small nature of the circuit boards: Overheating or
applying any pressure to a pad can de solder components on the other side of the board, or cause the pad itself
to become detached.
Power Supply Requirements
The power supply needed is nominally 5.6 to 18V DC, but any possible droop or ripple must be included: The
devices contain ‘brown-out’ detection, which may trigger if the supply voltage at the device drops below the 5.6
volts.
A single device consumes typically 40mA with a 350
Ω
gauge connected (except RS232-output units, which use about
10mA more).
An installation should therefore assume at least 60mA per unit, and allow for extra current being taken at power-on
(though supply voltage can safely drop temporarily), and for possible voltage drops in long cables.
Any power-supply ripple should be below 100mV, and supply arrangements should provide current limiting for fault
conditions (see
Electrical Protection,
above).
Cable Requirements
Strain Gauge input (DSC)
For optimal performance twin twisted pair with individual shields is recommended, this gives good noise immunity.
Maximum length should not exceed 20m. Normal 4 core shielded cable can be used in areas of low electromagnetic
noise.
Power and Communication
Again, twin twisted pair cable is recommended for this. The cable should have the following characteristics.
•
Twisted-pair with independent shields
•
Characteristic impedance 50-150 ohms.
•
Core to core and core to shield capacitance below 300pF/m
A suitable type is BICC Brand-Rex BE56723 (also equivalent to Belden type 8723).
In the UK, this is available from Farnell, part number 118-2117