Cardinal 205 Installation And Technical Manual page 12

SITE PREPARATION REQUIREMENTS, CONT.
Electrical Noise Interference
To prevent electrical noise interference, make certain all other wall outlets for use with air
conditioning and heating equipment, lighting or other equipment with heavily inductive loads,
such as welders, motors and solenoids are on circuits separate from the indicator. Many of
these disturbances originate within the building itself and can seriously affect the operation of
the indicator. These sources of disturbances must be identified and steps must be taken to
prevent possible adverse effects on the indicator. Examples of available alternatives include
isolation transformers, power regulators, uninterruptible power supplies, or simple line filters.
Transient Suppression
The following recommendations will help to reduce transients:
 Always use shielded cables to connect signal wires to the weight indicator.
 Secure the cables in the cable clips provided inside the indicator.
 Connect the cable shield (indicator end only) to a ground point inside the indicator. Keep
wires that extend beyond the shield as short as possible.
 Do not run load cell or signal cables from the weight indicator along side or parallel to
wiring carrying AC power. If unavoidable, position the load cell and signal cables a
minimum of 24" away from all AC wiring.
 Always use arc suppressors across all AC power relay contacts (see recommendations at
http://www.paktron.com/pdf/Quencharch_QRL.pdf).
 Use zero voltage switching relays, optically isolated if possible.
RFI Immunity
The operation of sensitive electronic equipment can be adversely affected by RF (Radio
Frequency) radio transmissions. Digital weight indicators are one such type of equipment.
Radio transmissions come from things like hand-held radio transmitters and cell phones. One
symptom of RFI (Radio Frequency Interference) in a digital weight indicator is weight indication
instability during a radio transmission.
Cardinal digital weight indicators are designed with special grounding and RFI shielding to
achieve a high degree of immunity to common RFI. To maximize the digital weight indicator's
immunity to radio transmissions, follow these guidelines:
1. ALWAYS use shielded cable for all I/O (Input/Output) connections to the digital weight
indicator.
2. NEVER operate any radio transmitter within 2 meters (~6ft.) of the weight indicator.
3. NEVER connect un-terminated serial, digital, or analog I/O cables to the internal printed
circuit boards of the digital weight indicator.
4. KEEP the intended external I/O device connected to I/O cables entering the digital
weight indicator.
5. ALWAYS connect the shield of the shielded cable to the indicator back panel gland
connector or other closest ground terminal inside the indicator.
6. ALWAYS connect the shield of the shielded I/O cable at the indicator end only. Leave
the shield unconnected at the I/O device.
8200-M129-O1 Rev D  205 Installation & Technical
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