Hach 366 Serie Manual Básico Del Usuario página 17

4.5.2 3662EX (in hazardous area)
The power for the 3662EX instrument in the hazardous area must be provided through a safety barrier from the
safe area with a shielded cable.
The power source comes from the customer's installation. Connect a safety barrier (model ref.
32956), to the power supply output in the safe area. Maximum cable length allowed from safety
barrier to instrument is 999 m.
DC power connections for the 3662EX instrument are through the left cable gland. Attach the power
wires to the power filter block J11, and the cable shield to a ground screw (see
gland fitting on page 11).
+ +6.5 to +13.5 VDC (50 mA)
-- Ground.
PE Earth. This connection must be made to the ground screw on the left side of the instrument, using a 4 mm
diameter eyelet.
4.5.3 3662EX power supply cable requirements
The power supply cable from the safety barrier to the 3662EX instrument must meet the following
criteria:
Cable loop maximum resistance, Rc (max) = {(Ug - Ui (min))/ Imax} - Rb where:
• Ug = external supply voltage, in safe area
• Ui (min) = minimum input voltage of 3662EX = 6.5V (6.5V < Ui < 13.5V)
• Rb = internal resistance of safety barrier
• Imax = average current of 3662EX (Imax = 0.050A)
Maximum cable capacitance, Cc = Cext - Ceq where:
• Cext = maximum permissible capacitance of safety barrier
• Ceq = input capacitance of 3662EX (Ceq = 38nF)
Maximum cable inductance, Lc = Lext - Leq where:
• Lext = maximum permissible inductance of safety barrier
• Leq = input inductance of 3662EX (Leq = 1.92mH)
For example, with the safety barrier (model ref. 32956) and a 24 VDC power supply, the cable
requirement is as follows:
• Rb = 226 Ω, Cext = 132 nF, Lext = 4 mH)
• Rc (max) = {(24 - 6.5)/ 0.050} - 226 = 124 Ω
• Cc = 132 - 38 = 94 nF
• Lc = 4 - 1.92 = 2.08 mH
Thus, for a 3662EX instrument installed 999 m. away (or closer) from a ref. 32956 safety barrier, the
cable must have a maximum loop resistance of 124 Ω, maximum capacitance of 94 nF, and
maximum inductance of 2.08 mH.
4.6 Analog and alarm output connections
4.6.1 Analog output and alarm cables in "Safe" area (3660EX)
4.6.1.1 Analog current output
Pass the cable through the cable gland. Attach the applicable output wires to the + and - terminals on
terminal block J18.
W A R N I N G
Waterproof cable
English 17