INSTALLING WIRING FOR MEASUREMENT AND
CONTROL
or
HOW TO (NOT TO) BUILD A LOT OF
Obscure Problems!
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Puzzlement
Frustration
Moan-Sob! |
AVOID COMMON RETURNS!!!
Shun!
Don't Use!
Eschew! |
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IF IT ALL BALANCES OUT, NO
PROBLEM -- IF UNBALANCED, WOE!
I1 = I2
V1 = V2 V3
= V4 etc. EVERYTHING BALANCES; NO NOISE
OR MEASUREMENT ERRORS.
PLACING WIRES IN WIRE WAYS
AND ON POLES REQUIRES SPECIAL SPACING
BE CAREFUL TO USE WIRE THAT
IS BIG ENOUGH FOR THE LOAD YOU PLAN TO CONNECT. THEN
TEST TO SEE THAT THE CORRECT VOLTAGE APPEARS AT THE
LOAD.
| VS = VC+VC+VL |
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VC IS THE LOSS IN THE
CONDUCTOR.
IT IS EQUAL TO THE RESISTANCE OF THE CONDUCTORS
TIMES THE CURRENT THROUGH THEM. |
IF YOU HAVE A RELAY THAT IS PICKED BY
100 MA, THE LOOP SUPPLY IS 24V, AND THE LINE RESISTANCE IS
20 OHMS, THE VOLTAGE ACROSS THE RELAY SHOULD BE:
VL = VS - VC-VC
22 = 24 - 2 |
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VC = (RC +
RC) I
2V = 20 OHMS x 0.1 AMP |
SEE YOUR NATIONAL ELECTRIC
CODE HANDBOOK FOR WIRE SIZING.
IF YOU WANT TO TEST NO SNEAK
CIRCUITS -- TEST IS EASY.
ANOTHER THING --
LOOSE CONNECTIONS, BAD CONNECTIONS, INTERMITTENT
CONNECTIONS, CORRODED CONNECTIONS, LOOSE SWAGE CONNECTORS,
COLD SOLDER JOINTS --
- TOUGH TO FIND
- WASTE TIME
- CREATE CONFUSION
SOME TIPS:
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