3M 724 Instructions Manual - Operator Monitoring -
5
The Model 724 monitor allows for the
selection of test voltages (9v or 16v)
and resistance limits (10 Megohms or
35 Megohms). The additional ranges
have been added to accommodate
global Electrical Static Discharge
requirements. Selection of the
operating parameters are left up to the
user’s discretion (See Section 4).
Operator Monitoring -
Single and Dual
Fig. 3 - Face of Model 724
The wrist strap monitoring function
is activated by plugging a wrist strap
dual conductor ground cord into either
one of the jacks on the 3M
™
Models
732/733 Dual Conductor Remote
Input Jack. If the resistance of the
wrist strap loop is within the limits of
the selected range (1.5 Megohms to
10 Megohms or 1.5 Megohms to 35
Megohms)* on the Model 724
Monitor, the cord, the wrist band, and
the contact to the arm of the wearer, it
is considered to be functioning
correctly. At this time, one of the
(OK) green lamps (1 or 2) will be
illuminated on the front of
the monitor.
If the resistance of the wrist strap
loop is higher than the selected range
(10 Megohms or 35 Megohms)* on the
724 monitor, an (OK) wrist strap green
lamp (1 or 2) extinguishes, and
a high wrist strap red lamp (H)
illuminates with an audible alarm. This
is an indication of a high resistance in
the cord band, or poor contact between
arm and band. If the resistance in the
loop is under 1.5 Megohms,* it is an
indication of a low resistance meaning
one or both current-limiting resistors
are bypassed. The low yellow lamp (L)
will flash and an (OK) green lamp
(1 or 2) will remain illuminated.
Caution
A low resistance condition can also
be caused by touching a grounded
object or by standing on a
conductive surface.
The wrist strap of a second operator
is measured in the same way. Operators
are identified by the two (OK) green
lamps (1 & 2). However, the same high
wrist strap red lamp (H) and low
yellow (L) lamps illuminate when a
fault is detected. The green lamp that
extinguishes identifies the operator that
is experiencing the fault condition.
* Resistance values are ±15%
3M 733 Remote Splitter Kit purchased separately.
OK #1
Operator
OK #2
Operator
Resistance High Operator
Resistance Low Operator
Resistance High
Work Surface