AW Gear Meters EMO-1005 - Manual (Page 37)

AW-Lake Company 8809 Industrial Drive, Franksville, WI 53126  web: www.awgearmeters.com
 Tel: 262-884-9800  Fax: 262-884-9810  Email: [email protected]
REV. 1a 05/98 EMO-1005 Manual.DOC
36
IMPORTANT! NEVER CONNECT THE SHIELD TO GROUND IN BOTH ENDS !
THAT COULD PRODUCE UNWANTED OSCILLATIONS IN THE SIGNAL WIRES!
HARDWARE HINTS
The EMO-1005 internally has 1-5 microprocessors therefore, it is very important to pay attention to
proper signal wiring and shielding.
SIGNALS AND SHIELDING
The standard EMO-1005 is delivered with two frequency inputs. Pin 4 of any channel card is an
opto-coupler input where 5-30Volts turn on the opto-coupler. This input is used mainly for the ZHM
series flowmeters distributed by the AW Company. The frequency return from a ZHM meter can be
directly connected to this input. Pin 3 is an adjustable threshold input. This input has the ability to be
adjusted to three different sensitivity levels. The highest level is 3.25Volts. This is used for signals that
have a amplitude swing from 3.5-50Volts maximum. This means that the incoming wave form must
have an amplitude of at least 3.25V (3.5V is better). If the signal source is less that 3.5V the threshold
has to be adjusted lower. The next lower threshold is 1.7V. The lowest threshold is mainly used for
inductive pick-ups. This threshold is set at 50mV. Refer to drawing EMO10904, Appendix F, for the
location of the sensitivity adjustment jumpers. The frequency input signal should always be referenced
to the ground connection (pin 2). Most applications require signal shielding. A solid aluminum wrap
shielding will work fine. The shield should be connected to pin 2 on the respective channel terminal.
Do NOT connect the shielding at the transmitter.
GROUNDING CONSIDERATIONS
The grounding is the most important consideration in an installation where microprocessor technology
is applied. The EMO-1005 is a panel mounted unit and therefore the casing is connected to the
sub-panel. If the sub-panel is metal this should be grounded. This way the EMO-1005 housing is
grounded. If the sub-panel is non-conductive the rear panel terminal block for power supply, pin 1, can
be used for grounding.
In case of strong EMI (ElectroMagnetic Interference) it is recommended to use an EMI filter in the
110V/60Hz (220V/50- 60Hz) supply line. These filters can be purchased at any local electronic parts
supplier.
A few important hints:
- Always establish a solid ground in the installation.
- Place the EMO-1005 as close as possible to the central ground.
- Never pull the signal lines close to High-Voltage wires.
- Use shielding on all signal wires.
- Never plug an EMO-1005 in the same outlet with motor controls or lighting
circuits. A separate 110V line is recommended.