Environmental Measurement Japan Co., Ltd.

Atmospheric CO2 Gas Control Unit

AC-004 Instruction Manual

Table of Contents

1. Summary

2. Features and Functions

3. Installation and Setup

4. Parts List

5. Wiring and Piping Diagrams

6. Contact

1. Summary

This all-in-one unit features various functions necessary for the operation of an external NDIR CO2 analyzer. The unit features a combination of sample gas suction, filtration, flow rate display, flow rate control, and piping for standard gases.

Outer dimensions are matched to those of NDIR model LI-7000, manufactured by the US company LI-COR.

Caution: The AC-004 is a special version of its sister unit, the AC-003. The AC-004 includes a heater but does not include the PC link unit, cover, NDIR/AC-003 control software, and DC power supply found in the AC-003. When using the unit, be sure to use all appropriate peripheral devices.

2. Features and Functions


Front Panel (Left)

Figure 1: Front Panel (Left)

1. Reference gas flow rate: This shows the flow rate of the reference gas.

2. Reference gas flow rate set knob: This knob is used to adjust the reference gas flow rate. Turn clockwise to increase the flow rate.

3. Sample gas flow rate display: This display calculates and displays a flow rate based on the signal from the mass flow meter.

4. Sample gas flow rate adjustment knob: This knob is used to adjust the sample gas flow rate. Turn clockwise to increase flow rate.

5. Sample gas filter: EMJ Turn-flow type gas filter. Element diameter is 55mm.

Front Panel (Right)

Figure 2: Front Panel (Right)

6. Zero gas flow rate adjustment knob: This knob is used to adjust the flow rate of the zero gas. Turn clockwise to increase flow rate.

7. Span gas flow rate adjustment knob: This knob is used to adjust the flow rate of the span gas. Turn clockwise to increase flow rate.

Right Side Panel

Figure 3: Right Side Panel

8. Sample gas suction inlet size is 1/4 inch (6.35mm): Please connect to the suction tube.

9. Sample gas exhaust #1 outlet size is 1/4 inch (6.35mm): Typically nothing is connected here.

10. Sample gas exhaust #2 outlet size is 1/4 inch (6.35mm): Typically nothing is connected here. During correction the sample gas is exhausted here.

11. Please connect the span gas supply (from the span gas tank) here.

12. Please connect the zero gas supply (from the zero gas tank) here.

  1. Please connect the reference gas supply (from the reference gas tank) here.

(Note it is permissible to branch off the span gas or zero gas supply to provide the reference gas. )

Left Side Panel

Figure 4: Left Side Panel

14. Reference gas outlet size is 1/4 inch (6.35mm): Connect to NDIR reference cell inlet.

15. Sample gas outlet size is 1/4 inch (6.35mm): Connect to the NDIR sample cell inlet.


Top Side Terminal Array

Figure 5: Top Side Terminal Array

D1: Mass Flow Meter +12Volts DC

D2: Mass Flow Meter COM DC

D3: Mass Flow Meter -12Volts DC

D4: Electromagnetic Valve +12 Volts DC for both 3SV1 and 3SV2

D5: Electromagnetic Valve COM DC for both 3SV1 and 3SV2

D6: Electromagnetic Valve 2SV1 +12 Volts DC

D7: Electromagnetic Valve 2SV1 COM DC

D8: Electromagnetic Valve 2SV2 +12 Volts DC

D9: Electromagnetic Valve 2SV2 COM DC

A1: Heater 100V AC

A2: Pump 100V AC

A3: Sample Gas Flow Rate Display 100 Volts AC

3: Installation and Setup

In this section the procedures for installing and setting up the AC-0014 are described.

1. Installing the AC-004 Unit

Figure 6: Dimensions of Right Side Panel

Rubber feet are attached to the bottom of the unit. Typically the unit would simply be placed on a flat surface. When installing the unit in a sealed container such as a cubicle, the piping will have to be guided into the container. However, this task can be made avoided by attaching the right side panel (Figure 3) to the interior wall of the sealed box. If this is the case, use the four M5 tap holes provided on the right-side panel. Dimensions are referenced below.

2. About the Piping

For information about the zero gas, reference gas, span gas, or sample gas piping, please refer to Section 2. Features and Functions.

Caution: when using this unit as an eddy correlation system:

When using the AC-004 as an eddy correlation system, it is critical that system-wide flow rate is not allowed to drop. Though the internal piping in the AC-004 has been carefully designed not to drop the flow rate, external NDIR and other piping may significantly affect the flow rate. Keep in mind carefully the following points.

2.1. When connecting the AC-004 to the external NDIR, avoid using small internal diameter (ID) tubing such as Bev-A-Line tubing. Though they do not bend as easily, tubing with larger internal diameters such as Teflon tubing (1/4” ID) and stainless steel tubing are recommended. As a general rule of thumb, avoid any tubing with an ID less than 4mm.

2.2. Tube circularity may become an issue when using shape-retaining tubing such as Dekabon tubing. Be careful of extreme bends and gas leaks when connicting this tubing. The small gas leaks that occur particularly when such tubing is used under negative pressure can affect the measured value.

2.3. Confirm the power source voltage is the correct one. The AC-004 contains a diaphragm pump. This pump’s flow rate corresponds to the power source voltage, and any decrease in voltage will result in a decrease in flow rate.

3. Wiring

Refer to Section 2. Features and Functions for a description of the wiring in the unit.

Caution: The mass flow meter requires a +12V, COM, -12V supply.

4. Operation of the Electromagnetic Valves

Zero Correction ON: 2SV1, 3SV1, 3SV2

Span Correction ON: 2SV2, 3SV1, 3SV2

Measurement: All OFF

Caution: When there is no signal to the EM valve, the piping configuration defaults to the “Measure” mode. This is a fundamental design feature that allows measurements to be made even when the EM valves are not operational.

4. Parts List

Part #



Model #

Number Used

1 2-Way Electromagnetic Valve




2 3-Way Electromagnetic Valve




3 3-Way Electromagnetic Valve




4 Air Pump

Enomoto Micro Pump



5 Flow Meter (Reference)

Tokyo Keiso

P100-L0-4N-R2-C h F.S. 20mL/min


6 Flow Meter (Sample)

Tokyo Keiso



7 Turn-Flow Filter




  Filter Element

Advantec Toyo

PG-60(diameter 55mm) 100 sheets Pore size 0.5m m


  Stainless Steel Tubing (BA)


SUS 316 BA1/4


  Stainless Steel Tubing (BA)


SUS 316 BA1/8


8 Needle Valve


SS-SS2 (Straight)


9 Needle Valve




10 Union T




11 Union T




11 Reducer




12 Bulkhead




13 Bulkhead




14 1/4 inch Male Connector




15 1/8 inch Male Connector




16 1/8inch Male Connector




21 Flow Rate Display (Sample Gas)

Watananbe Denki



22 Panel Heater




5. Piping Diagram

Figure 7: AC-004 Gas Piping Diagram

6. Contact

Claims and inquiries should be directed to the address below. Response will come swiftly. All responsibility for the AC-004 belongs to the following:

Designed and Built by Dr. Katayama Hiroyuki

Environmental Measurement Japan Co., Ltd.

6-5-1 Murasaki, Tikushino City, Fukuoka 818-0061, Japan

E-mail: katayama@environment.co.jp

Tel & Fax Outside Japan: +81-92-920-1067

Tel and Fax Inside Japan: 092-920-1067