Altek 334A User Manual

Loop Calibrator

Model 334A

• All milliamp loop functions

Source milliamps
Simulate two-wire transmitters
Read milliamp outputs
Power & measure two-wire transmitters
Read DC Volts to check power supplies

• Compact and lightweight

Easy to carry – less than a pound
Includes padded nylon carrying case with
shoulder strap and belt loop

• Accuracy to ±0.03%

Within ±0.02 mA from 4 to 20 mA

• Long lasting alkaline batteries

Three “9V” batteries last many shifts
Optional AC adaptor for bench use

• “Quik-Chek®” Switch

Instantly output 4.00 and 20.00 mA

• Milliamp or % display

Source or Read from 0.00 to 24.00 mA or
from -25.0 to +125.0% of 4 to 20 mA

• Overload protected

Withstands 135 Volts AC/DC without fuses

Easy to use

The Altek Model 334Awill check, calibrate and
measure all your current signal instruments in a 4 to
20 milliamp DC loop. Use at every point in your loop.
Source & Read 0.00 to 24.00 mA, Simulate a 2-wire
transmitter or use the Model 334A to simultaneously
power & measure your 2-wire transmitters. Toggle the
display to show milliamps or percent of 4 to 20.

Source milliamps

Calibrate recorders, digital indicators, stroke valves or
any other instruments that get their input from a 4 to
20 mA loop. Easily set any value to within 0.01 mA
with the speed sensitive digital potentiometer.

Recall output setting

The “Quik-Chek” switch provides rapid checking of

4.00, 20.00 and a third point between 0.00 to 24.00
mA.

Calibrate using loop power

Check loop wiring and receivers by using the Model
334A in place of a 2-wire transmitter. Simulate a
changing process input to check loop response and
control settings. The Model 334A uses any loop power
from 3 to 45V DC.

Read loop current

Check controller outputs or measure the milliamp
signal anywhere in the loop. The Model 334A
measures 0.00 to 24.00 mA signals with much greater
accuracy than a typical multimeter. Toggle the display
to show milliamps or percent of 4 to 20.

Power and measure 2-wire transmitters

Simultaneously measure the output of a 2-wire
transmitter while using the internal batteries to supply
up to 27V DC to power the transmitter. Handy for
checking transmitters in the field or on the bench.

Read DC Volts

Measure from -99.99 to +99.99 VDC with 10mV
resolution. Use it to check loop power supplies, I/V
converters, 1 to 5 Volt signals and battery voltages.

General description

Operating instructions

Recalling Quik-Chek outputs

Instantly output 4.00 or 20.00 mA by moving the
Quik-Chek switch to the 4.00mA / 0.0% position or

20.00mA / 100.0% position. For fast three point
checks select the ADJUST position. The Model 334A
automatically remembers the last ADJUST value,
even with the power off.

Note: The same ADJUST value is stored for both
mA and %. The recalled value will be displayed in
the units you have selected.

Open loops

The display will indicate 0.00 mA or -25.0% if there
is an open loop or if the polarity is reversed. Check
all the connections in the loop or try reversing the
leads.

Power transmitter

Adjusting the SOURCE output to full scale supplies
a nominal 24V DC to power a two wire tranmitter
while simultaneously displaying the 4 to 20 mA
output of the transmitter.

Read milliamps

Select read milliamps by moving the slide switch to
mA or % 4 to 20 mA and moving the left hand toggle
switch to READ. Place the Model 334A in the loop in
series with the current to be measured.

Read DC Volts

Select read DC Volts by moving the slide switch to
READ VDC and moving the left hand toggle switch
to READ. Clip the leads across the voltage to be
measured.

Setting up valves

When setting up a valve it is important to correctly
set the end stops. Use the 334A to supply the 4 to
20 mA control signal to stroke the valve. Select
SOURCE to output using the internal batteries as
the power souce or 2-WIRE SIMULATOR to stroke
the valve using an external power supply.

1) Disconnect the 4-20 mA control wires from the
Current-to-Pressure (I/P) converter or the
actuator.

2) Connect the 334A following the connection
diagrams on the next page for SOURCE or
SIMULATE 2-WIRE TRANSMITTERS.

3) Move the Quik-Chek switch to 4.00mA/0.0% and
adjust the fully closed stop on the actuator.

4) Turn the 334A’s knob slowly counterclockwise
and verify that the actuator and valve don’t move.
Repeat steps 3 & 4 until no movement is
detected.

5) Move the Quik-Chek switch to ADJUST and
quickly back to 4.00mA/0.0% then turn the 334A’s
knob clockwise. The actuator and valve should
begin to move.

6) Move the Quik-Chek switch to 20.00mA/100.0%
and adjust the fully open stop on the actuator.

7) Turn the 334A’s knob slowly clockwise and verify
that the actuator and valve don’t move. Repeat
steps 6 & 7 until no movement is detected.

8) Move the Quik-Chek switch to ADJUST and
quickly back to 20.00mA/100.0% then turn the
334A’s knob counterclockwise. The actuator and
valve should begin to move.

Turn-on

Move the slide switch left to mA to calibrate in mA or
right to % 4 TO 20 mA to calibrate in percent. The
left hand toggle switch is then used to select
SOURCE, READ or 2 WIRE TRANSMITTER
SIMULATOR.

To READ DC VOLTS move the slide switch all the
way to the left and place the left hand toggle switch
to READ.

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Move the slide switch to OFF to turn the 334A off.

mA or %

Choose mA to display directly in milliamps. Select %
4 to 20 mA to display in percent of span for 4 to 20
mA loops. Percent is also used with chart recorders,
valves or current trips that display in percent.

100.0% 20.00 mA

75.0% 16.00 mA

50.0% 12.00 mA

25.0% 8.00 mA

0.0% 4.00 mA

To convert from Percent to Milliamps

Percent =(mA-4)/0.16

To convert from Milliamps to Percent

mA=Percent/6.25)+4

Changing batteries

Low battery is indicated by BAT on the display.
Approximately four hours of typical operation remain
before the 334A cannot supply the full output into a
load. When the batteries are too low for the 334A to
operate, the LCD blanks and Model 334A shuts itself
down. Turn the 334Aoff, remove the four screws
securing the housing and lift the calibrator out of the
housing. The three “9V” batteries are easily removed
and replaced (alkaline supplied and recommended).
Replace the calibrator in the housing and replace the
screws.

Out of range signals

Signals below 0 mA or open circuits are indicated by

0.00 mA (-25.0%) on the display. Signals above 52
mA are current limited by protection circuitry to
approximately 55.00 mA.

Keeping the process going

When an instrument in a critical control loop
develops a problem it is important to maintain control
of the process. The Model 334A can be temporarily
substituted for a faulty controller or transmitter to
provide a manual loading station. One technician
takes manual control of the process while a second
technician retrieves and configures a replacement
instrument.

Source milliamps or 2-wire
transmitter simulator

Select SOURCE to output from 0.00 to 24.00
milliamps using the internal batteries as the power
souce. Select 2-WIRE SIMULATOR to control the
current in loop that has an operating power supply.
To change the output value turn the speed sensitive
digital potentiometer (konb). The faster it is turned,
the faster the output will change. This function
operates in all three output positions (HI, SET & LO).

mA

%