Altek Model 941 Frequency Calibrator Manual

							ALTEK DATA SHEET
ALTEK INDUSTRIES CORP
GENERAL DESCRIPTION
941
MULTI-FREQUENCY CALIBRATOR
MODEL 941
Calibrate your turbine meters, frequency counters, vibration
systems, tachometers, vortex shedders, integrators and any
other frequency devices in the shop, plant or field. Measure from
0.01 Hz to 250.00 KHz with resolution down to 0.01Hz. For your
slower signals source or measure from 4.0 to 2000.0 Counts per
Minute (CPM) or from 10 to 20000 Counts per Hour (CPH).
Quickly indicate process signals...no more waiting around with
stopwatch and calculator.
“SOURCE MODE”  FUNCTION GENERATORSelect sine wave outputs to simulate vibration pickups and
variable speed drives and square waves to simulate flowmeters
and magnetic pickups. Any frequency from 0.01 Hz to 250.00
KHz can be sourced in four frequency ranges to calibrate
tachometers, counters, data loggers, turbine meters and
frequency transmitters. For low frequency applications such as
positive displacement flowmeters, Watt-hour meters, slow rate
integrators and assembly line counting, the Model 941 sources
signals as low as 1 CPH (0.0002777 Hz). Amplitude is adjust-
able from 50 millivolts to 12 Volts peak-to-peak.
Three “QUIK-CHEK” output values are remembered for each
range. Turn the knob to check trip points, controller action and
to control variable speed drives. The fast response 941 sets
quickly without overshoot but allows slow changes at your own
rate. Memory is retained for each range even when power is off.
“READ MODE MEASURES WIDE RANGE
OF FREQUENCIES  AND WAVEFORMSUse out in the field to check the signals from your  flowmeter
pickups, velocity and motion detectors, Frequencies can be
directly measured from 0.01 Hz to 250.00 KHz in four frequency
ranges.
Measure extremely slow frequencies (
						

							OPERATING INSTRUCTIONS
GENERAL
        TURN-ONEach time the Model 941 is turned on, the 
LCD will display all segments for about 1 
second. It then displays the currently 
selected waveform (Source Mode) for
approximately 3 seconds.
1) Move the power switch to SOURCE or READ. All segments on the LCD are 
turned on during self test.
2) (SOURCE MODE ONLY) The display will indicate the selected waveform for 3 
seconds. Repeatedly press or press and
hold the SCROLL/STORE pushbutton to 
change to the desired waveform.
3) (SOURCE MODE ONLY) The three QUIK- CHEK  frequency outputs will be the same 
as previously stored.  Each time a
different range is selected, the three
QUIK-CHEK outputs for that range will 
be recalled.
4) Move the mode switch to RANGE and repeatedly press or  press and hold the
SCROLL pushbutton to change to the 
desired frequency range.
5) Return the mode switch to FREQ/TRIG to source or read frequency signals.
  CONNECTIONS The Model 941 has built-in test leads with 
alligator clips for attachment to instruments 
or sensors with terminal blocks or flying
leads. An optional  BNC connector attaches
to instruments or sensors  equipped with
BNC’s for fast connections.
SOURCE MODESome receivers can only detect signals that go from positive to negative\
 
(Sine Wave or Zero Crossing Square Waves) while other receivers requir\
e 
only positive signals (Zero Based Square Waves). The Model 941 provide\
s
a choice of these outputs.
OPERATING HINTS
ALTEK INDUSTRIES CORP CHANGING BATTERY
Low battery is indicated by BAT on the LCD 
Display. Approximately 10 Hours of opera-
tion remain before the LCD goes blank and 
the Model 941 shuts itself down.  Turn the 
941 off, loosen the three captive screws
securing the battery compartment cover.
The six “AA” batteries are easily removed
and replaced. Replace the battery
compartment cover, tighten the screws and 
turn on when ready to use.
             RESET The Model 941 may be reset to the factory 
default setting. This will reset all the
“QUIK-CHEK” memories to  display 1000
and will set the output and trigger levels to
1 V p-p.
1) Press and hold the SCROLL/RESET pushbutton while turning the Model 941 on to
SOURCE or READ
2) Keep pressing the STORE pushbutton for 10 seconds
3) All segments on the LCD will remain displayed until the Model 941 has been
reset
FIELD & BENCH USE The Model 941 comes with a carrying case
and a built-in tilt stand/hanger. The 941 is
held securely in the case by Velcro
® even
with the carrying case open. The carrying
case also has a snap-on belt loop which can
also be looped around a pipe or rail.
The tilt stand is easily raised by pulling the
stand until it locks into place. The stand can
also be reversed for use as a hanger to 
suspend the Model 941.
›12
10.0
6.0 
3.0
1.0 
0.6
0.3 
0.1 
.06
.03 x10
SOURCE
8.8.8.8.8
OVER 
MAX 
HI 
LO 
MIN  
UNDER 
  
GATE READ
BAT 
MHz kHz
CPM
CPHSEC %
TOTAL
CUSTOM
SCROLL
STORE             RESET
ROCHESTER NY 14623ALTEK  MODEL 941
10.0
6.0 
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.03 x1
SOURCE109.41kHz
FREQUENCY CALIBRA TORSOURCEREADOFFLEVEL
FREQ RANGE X1/X10
TRIG
RANGE HI
SET LO MAX
READ MIN
SCROLLSTORE         RESET9VDC
SYMPTOM CHECK     SOLUTIONLack of 
Response 
Wrong Range 
Lack of 
response or 
jittery signal Make sure all power and signals 
are properly connected. 
Turn Model 941 OFF and back 
on to SOURCE. Repeatedly
press the SCROLL/STORE 
pushbutton until the correct 
waveform is displayed. 
Move the mode switch to 
RANGE and press the SCROLL/
RESET pushbutton until the cor- 
rect range appears in the LCD. 
Move the mode switch to LEVEL 
and turn the knob while observ-
ing the logaristhimic bar graph 
to match the input level of the 
device being calibrated. Return
the mode switch to FREQ.
Connections 
Waveform 
Range 
Peak Voltage
READ MODEIn order for the Model 941 to obtain the most accurate readings you 
must correctly set the ATTENUATOR, TRIGGER LEVEL and RANGE.
Signals from 50mV to over 240 Volts p-p, with or without DC offsets
can be displayed.
SYMPTOM CHECK      SOLUTION
GATE on LCD, 
Display shows 0.0 
OVER/UNDER 
Range on LCD 
Unstable reading Make sure all power and sig- 
nals are properly connected. 
Set at x1 for signals from 50mV to 
12 Volts p-p,  x10 for signals over 
12 V p-p. 
Turn knob until GATE pulses 
and readings are displayed. 
Small signals with large DC off- 
sets may require a series ca- 
pacitor. 
Move the mode switch to 
RANGE and press the
SCROLL/RESET pushbutton 
until the correct range appears 
in the LCD. 
Turn knob until GATE pulses 
and readings are displayed.
Connections 
Attenuator 
Input level 
DC Offset 
Range 
Trigger Level
CPM/CPH CONVERSIONS
To Convert From:   To:          Divide By:
CPM      Hz   60 
CPH      Hz 3600 To Convert From:   To:         Multiply By:
  Hz     CPM   60
  Hz     CPH 3600 
						

							OUT OF RANGE SIGNALSFrequencies above or below those available 
for the currently selected range will be
indicated by OVER and UNDER on the 
display (See OPERATING HINTS).
OPERATING INSTRUCTIONS
FREQUENCY OUTPUT (SOURCE MODE)
         SOURCE
1) Move the POWER switch to SOURCE 
2) Move the mode switch to RANGE andrepeatedly press or press and hold the 
SCROLL/STORE pushbutton to change
to the desired frequency range. Return the 
mode switch to FREQ.
3) Move the mode switch to LEVEL (AMPLI- TUDE) and turn the Digipot (Knob) until
the logrithmic bargraph on the display 
reaches the desired level.Return the mode
switch to FREQ.
4) Connect the Model 941 to the input termi- nals of the instrument or meter to be 
calibrated
5) Adjust the digital pot to the desired output value or QUIK-CHEK with previously
stored frequency outputs (see below)
Whenever SOURCE mode is selected the
word SOURCE will appear on the LCD 
display.  To change the output value, turn the
speed sensitive digital pot.  Turning the pot 
slowly will cause a gradual change in the 
output. A faster change will occur when the 
pot is turned faster. This function operates in 
all three output positions (HI, SET & LO).           STORE
1) Switch to HI or LO 
2) Turn the digital pot to desired value 
3) Press the STORE/SCROLL pushbuttonThe LCD will flash once to show that the 
value was saved
If a value is in the SET position and you want
that value stored in HI or LO, press and hold 
the STORE/SCROLL pushbutton while
moving the switch to HI or LO. The display will 
flash once to indicate the value has been 
stored. Then release the STORE/SCROLL
button.
Hint:  Pressing the STORE/SCROLL pushbutton will disable the
Model 941s frequency generator. Releasing the pushbutton will 
re-enable the output.This is useful for synchronizing with  displays for
slow (< 1 Hz) signals.
ALTEK INDUSTRIES CORP
FREQUENCY COUNTER (READ MODE)
            READ 1) Move the POWER switch to READ 
2) Move the mode switch to RANGE andrepeatedly press or press and hold the 
SCROLL/RESET pushbutton to change
to the desired frequency range. Return the 
mode switch to TRIG.
3) Switch the MODE switch to LEVEL (AMPLITUDE) to toggle between x1 & x10
attenuation (Use x1 for signals from 30 
mV to 12 V p-p, x10 for signals from 12 V
to 240V p-p). Return the mode switch to 
TRIG.
4) Connect the Model 941 to the output of the instrument or sensor to be measured.
5) Adjust the trigger level to obtain a stable frequency reading by turning the Digipot
(knob). A bargraph on the display will 
show the approximate trigger level.
6) Use the “QUIK-CHEK” switch to display present reading, MAXimum or MINimum
frequency.
The word GATE will appear on the display 
whenever the Model 941 is measuring the 
frequency signal and will flash each time the
displayed reading is updated.          MIN/MAX
To read the Maximum or Minimum frequen-
cies since READ mode was entered, simply 
switch to MAX or MIN. The value will appear 
on the LCD along with the word MAX or MIN.
The MAX/MIN values are automatically 
updated and may be viewed at any time 
without disturbing the other values. Pressing
the RESET/SCROLL pushbutton will cause 
the 941 to stop counting frequencies and will 
display zeros. Upon releasing the RESET/
SCROLL  the Model 941 will display GATE, 
resume counting frequencies and update the 
MAX & MIN values as the measured
frequency changes.
CPM
CPH
PERIOD READINGS Select Counts-per-Minute (CPM) or Counts-
per-Hour (CPH) to measure slow frequency 
signals. Frequencies as low as 0.1 CPM 
(0.001666 Hz) and 10 CPH (0.002777 Hz)
can be measured (See CPM/CPH CONVER- 
SIONS for conversion factors).    TRIGGER LEVEL
The adjustable TRIGGER LEVEL is used in 
measurements of noisy signals, AC signals 
superimposed on DC levels and to select
Voltage threshold for all other signals. 
The bargraph on the display shows the 
approximate level from 0 to over 12 V positive
peak with the attenuator set at x1. This 
bargraph should be read as 0 to over 120 V 
positive peak with the attenuator set at x10.
For quickest readings, determine or estimate 
the voltage level to be  detected and set the
ATTENUATOR and  TRIGGER LEVEL to
match.
OVER
 UNDER
Isolated dry contact, open collector transis- 
tor or opto-isolated frequencies may be
measured with the Model 941 with the
optional DRY CONTACT MODULE (Model 
C-41) or with the circuit shown. In  order
to detect contact opening or closing, an exter- 
nal battery or power supply, in series with a
5000 Ohm resistor, may be used. Select
connection  polarity to provide desired signal
upon contact transfer.  Relay or switch
contacts may require a resistor-capacitor
filter in order to eliminate contact bounce
errors. Typical filter values for mechanical
contacts are 10 K Ohms and 0.1 microfarads.READING DRY CONTACTS
   QUIK-CHEK
Any time you need a stored value just throw 
the QUIK-CHEK  switch. Any value in the 
frequency range may be stored in HI & LO.
The Model 941 remembers the HI, LO and 
SET values for all ranges (18 memories) for 
you with the power on or off. Each time a
different frequency range is selected, the last 
three QUIK-CHEK  values for that type will be 
recalled.
SOURCESCROLL
STORE             RESET
HI
SETLOW
MAXREAD MIN
ROCHESTER NY 14623ALTEK  MODEL 941
10.0
6.0 
3.0
1.0 
0.6
0.3 
0.1 
.06
.03 x1
SOURCE485.3CPM
FREQUENCY CALIBRA TORSOURCEREADOFFLEVEL
FREQ RANGE X1/X10
TRIG
RANGE HI
SET LO MAX
READ MIN
SCROLLSTORE         RESET9VDC
5000 Ohm
DRY
CONTACT
1 to 24 VDC 10 K0.1
READ
›
12
10.0 6.0 
3.0
1.0 
0.6
0.3 
0.1 
.06
.03 x10O 
M
H 
LO
M
U 
 
G 
						

							SPECIFICATIONS
Variable Speed Drives 
Telemetry Systems 
Event Recorders 
Vibration Monitors 
Totalizers 
Data Loggers 
Velocity Detectors
Magnetic Pickups 
DC Contact Closures
Turbine Flowmeters
Vortex Shedders 
Positive Displacement Flowmeters 
Watt-Hour Meters 
V to F and F to V Converters 
Integrators 
Tachometers
Uninterruptable Power Supplies 
Counters 
Frequency Transmitters
TYPICAL APPLICATIONS
(Unless otherwise indicated, specifications are in 
±% of Reading @ 23 °C)
TYPICAL INDUSTRIES
Chemical Plants 
Petroleum Refineries 
Food Processing 
Pipelines 
Utilities 
Water & Waste Treatment 
Public Works
Steel Mills 
Paper Mills Textile Mills
Automotive Plants 
Aerospace 
Pharmaceutical 
Glass & Ceramics 
Metrology 
Beverages
Plastics 
Machinery 
Ordinance 
Computers
THREE YEAR WARRANTYOur equipment is guaranteed against defective material and work- 
manship (excluding batteries) for a period of three years from date of\
shipment. Claims under guarantee can be made by returning the
equipment prepaid to our factory. The equipment will be replaced,
repaired or adjusted at our option. The liability of Altek is restricted\
 to
that given under our guarantee. No responsibility is accepted for
damage, loss or other expense incurred through sale or use of our
equipment. Under no condition shall Altek be liable for any special,
incidental or consequential damage.
ORDERING INFORMATION       Part No.
MODEL 941 FREQUENCY CALIBRATOR               941 
WITH OPTIONAL BNC CONNECTOR           941-BNC 
Included with each Model 941 are:
Carrying Case (Part No. 09-3784) 
NIST Traceable Certificate and Three Year Warranty
OPTIONAL ACCESSORIES       Part No.
AC ADAPTOR: 120 VAC, 50/60 Hz           9V-0120 
AC ADAPTOR: 240 VAC, 50/60 Hz           9V-0240 
DRY CONTACT MODULE             C-41
AVAILABLE FROM:
© May 1996 Altek Industries Corp
RANGES
RANGE        SOURCE         READ GATE TIME 
  KHz  0.01 TO 250.00   0.01 TO 250.00 0.2 seconds 
  KHz                 0.001 TO 99.999 0.001 TO 99.999   1 second 
   Hz    0.1 TO 9999.9     0.1 TO 9999.9   1 period
   Hz  0.01 TO 999.99   0.01 TO 999.99   1 period 
 CPM    0.1 TO 2000.0     0.1 TO 2000.0   1 period 
 CPH       1 TO 20000      10 TO 20000   1 period
GENERALFREQUENCY STABILITY: 80 hours 
SOURCE MODE: 
Nominal >50 hours at 250 KHz at 12V p-p
LOW BATTERY: “BAT” indication on the display at 6.5 V nominal,
approximate 10 hours left. Batteries should be removed when storing 
unit >3 months. 
ATTENUATOR: Logarithmic for smooth input/output signal level 
control 
OPERATING TEMPERATURE RANGE: -5 to +140 °F (-20 to +60 °C)
STORAGE TEMPERATURE RANGE: -13 to +149 °F  (-25 to +65 °C)
RELATIVE HUMIDITY: 10 to 90%, non-condensing for 24 hours
WARM UP TIME: 5 seconds to rated accuracy 
OVERALL SIZE: 7
3/16 x 4 x 27/16 inches (183 x 102 x 62 mm)
WEIGHT: 1lb, 7oz (0.650 kg)
READ MODEACCURACY:  ±(0.001% of reading + 1 LSD)
SENSITIVITY: Triggers on positive peaks down to 40 mV peak, DC 
coupled 
MAXIMUM USABLE INPUT VOLTAGE: 240 VAC 
MINIMUM PULSE WIDTH: 2 microseconds 
INPUT IMPEDANCE: > 1 Meg Ohm + 60pF 
TRIGGER LEVEL ADJUSTMENT: x1 & x10 Attenuator plus logarithmic 
control 
NOTE: High signal noise and low slew rate (Volts-per-second) may affec\
t 
reading uncertainty
SOURCE MODEACCURACY:  ±0.001% of reading
OUTPUT WAVEFORMS: Sine, Zero Based Square, and Zero 
Centered Square Waves 
OUTPUT AMPLITUDE: 50 mV to 12 V p-p, 50%  ±1% duty cycle
RISETIME: