Monarch Instrument ACT-3 - Manual (Page 8)

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1.2.1 Auto Ranging
If the instrument is set to auto range (AUTO), it will always display data to the maximum
resolution, utilizing all five digits in the display. The display is always left justified, that is
the data always begins in the left most digit position and the decimal point moves to the right
with each increasing decade. The value 100 is thus indicated as “100.00”. The resolution then
varies from 0.0001 below 10 to 10 above 100,000.
NOTE: In order to display values in excess of 99,999 with only 5 digits, all the decimal
points light for values between 100,000 and 999,990, effectively indicating that
the displayed value needs to be multiplied by 10 to get the correct reading.
In the Auto ranging mode the decimal point is always visible, and zero is indicated as “0.0”.
1.2.2 Fixed Decimal Point
If the instrument is set to have a fixed decimal point (SET), the decimal point is effectively
fixed on the extreme right hand side of the display. The decimal point it is not actually visible
in this position. In fact, the decimal point is not visible at all for readings less than 100,000.
In this case the display is always right justified with unused digits to the left being blanked.
The value 100 is thus displayed as “100” with a resolution of ±½. For values above 99,999
all the decimal points light as in the auto ranging mode and the resolution of the display is 10.
NOTE: The display is always rounded to the nearest whole number. A value of 100.3 is
displayed as 100 while a value of 100.7 would be displayed as 101, maintaining
the accuracy, as well as the resolution to ±½.
1.3 Limits (Alarms)
The ACT-3 and ACT-3A have two independent alarm set points, referred to as LIMIT 1 and
LIMIT 2 (Set 1 and Set 2 on the menu). These limits are fully programmable by the user (unless
the write protect option has been set). The limits may be set as high or low with an option of low
limit lockout, latching or non-latching at any value. The limits are accurate to better than ±0.1%
of the set point value. Refer to Section 3.0 for the limit response time. The hysteresis is also
programmable at any value from 0.0001 to 99.999% of the set point value. The actual output
from these alarms is a set of form C, dry contacts, accessible via barrier strip screw terminals on
the rear panel. These contacts are capable of switching 1 A at 250 Vac. When the unit is making
measurements, the limits can be viewed by pressing the UP (
∧∧∧∧∧) button for LIMIT 1 or the DOWN
( ∨∨∨∨∨) button for LIMIT 2. The display will return to normal after a few seconds. Refer to Section
5.0 to set limit set points.
1.3.1 Latching vs. Non-Latching Limits
A latching limit is one which, when the alarm trips, remains in this condition regardless of
what the input may do. This tripped limit needs to be manually reset by the operator to
restore it back to its normal position. A non-latching limit on the other hand will automatically
reset itself when the input no longer exceeds the set point, either high or low. The user can
program each limit to be latching or non-latching. Refer to Section 6.0.
1.3.2 Hysteresis
Hysteresis is only applicable to non-latching limits. Hysteresis is a value that is added to
the set point (in the case of a low limit) or subtracted from the set point (in the case of a high
limit) so that this new value (set point + hysteresis) becomes the reset point for the alarm.
The primary purpose of this function is to prevent the alarm relays from chattering when the
input value remains very close to the set point. Hysteresis is generally expressed as a
percentage of the set point. Whenever the user sets or changes a set point, the instrument
automatically calculates a 5% hysteresis value. Suppose you had set a high limit at 100, the
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Scale Factor Of Comment Gives Read Outs In
( π x d”) circumference of wheel inches per second
( π x d”) ÷ 36 36 inches in a yard yards per second
(( π x d”) ÷ 36) x 60 60 seconds in a minute yards per minute
5.2360 x d” multiplying the known yards per minute
Say the diameter (d) is 10 inches. We get that pulses per second = 52.36 yards per minute and our scale
factor is thus 52.36 for a 10 inch diameter shaft.
2) Suppose we have a shaft turning on a conveyor and we know that for each turn of the shaft, the
conveyor moves X inches and we get one pulse into the tachometer. This step eliminates having
to calculate the circumference. If we wanted to know speed in meters per second then review
the following.
The Input is measured in pulses per second. There are X inches per pulse, so:
Scale Factor of Comment Scales Display To
X inches per pulse inches per second
X x 0.914402 ÷ 36 1 yard = 0.914402 meters meters per second
36 inches in a yard
X x 0.0254 multiply out meters per second
The scale factor is thus 0.0254 x X (where X is in inches).
3) Suppose we have wheel of d inches in diameter. This wheel turns the tire on a motor vehicle. We
get one pulse into the tachometer for each revolution of the drive wheel. We want the display
in miles per hour. We ignore slip.
NOTE: For more than one pulse per revolution, simply divide the scale factor you get for one pulse
by the number of actual pulses per revolution.
Scale Factor of Comment Scales Display To
( π x d”) circumference of wheel inches per second
( π x d”) ÷ (5280 x 12) 1 mile = 5280 feet miles per second
12 inches = 1 foot
( π x d”) ÷ 63360 multiply out miles per second
( π x d” ÷ 63360) x 3600 1 hour = 3600 seconds miles per hour
0.1785 x d multiply out miles per hour
To enter the actual scale factor into the tachometer, do the following:
Turn the tachometer on. Assuming there is no input, the display will show 0. Press and hold in the
SET and RESET buttons and then press the RECALL button once. Release all buttons and the
display should show tyPE. Press the SET button once and the unit will display its current mode of
operation. Press and release the UP (
∧∧∧∧∧) button until the display shows SCALE, the press the SET
button once. The display will show donE and the tyPE.
Press and release the UP ( ∧∧∧∧∧) button until the word SCALE appears in the display, then press the SET
button once. The display will show the current scale factor value with the right-most digit flashing.
The UP (
∧∧∧∧∧) and DOWN (∨∨∨∨∨) buttons will change the flashing digit, the SET button moves the flashing
digit and the RECALL button changes the decimal point. Using these buttons, alter the display to
indicate the scale factor you want.