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Flow Reading Questions
- The meter's flow reading is approximately fixed either near zero or near full scale regardless of actual line flow.
The differential pressure sensor may be damaged. Avoid installations that can subject sensor to pressure drops in excess of 75 psid (15 psid for “Whisper” Series instruments). A common cause of this problem is instantaneous application of high-pressure gas as from a snap acting solenoid valve upstream of the meter. Damage due to excessive pressure differential is not covered by warranty.
- The controller's flow reading is approximately fixed either near zero or near full scale regardless of actual line flow.
Differential pressure sensor may be damaged. Avoid installations that can subject sensor to pressure drops in excess of 75 psid (15 psid for “Whisper” Series instruments). While in most cases the valve will help to protect the sensor against large pressure drops, a sudden change in pressures can subject the sensor to high pressure drops if the valve does not have enough time to adjust. Damage due to excessive pressure differential is not covered by warranty.
- The meter's flow reading is fixed at zero regardless of actual flow rate.
Alicat mass flow meters are equipped with a tare function via grounding a specified pin. Please check electrical connections to ensure this pin is not grounded. Pin out diagrams are available in the back of the manual for your reference.
- The meter reads negative flow when there is a confirmed no flow condition.
This is an indication of an improper tare. If the meter is tared while there is flow, that flow is accepted as zero flow. When an actual zero flow condition exists, the meter will read a negative flow. Simply re-tare at the confirmed zero flow condition. Also note that while the meter is intended for positive flow, it will read negative flow with reasonable accuracy (it is not calibrated for bidirectional flow) and no damage will result.
- The flow flutters or is jumpy.
The meters are very fast and will pick up any actual flow fluctuations such as from a diaphragm pump, etc. Also, inspect the inside of the upstream connection for debris such a Teflon tape shreds. Mass flow devices feature a programmable geometric running average (GRA) for both pressure and flow rate measurements that can aid in allowing fluctuating flow to be read. This can be adjusted via the front panel or serial communications.
- The meter does not agree with another meter I have in line.
Volumetric meters will often not agree with one another when put in series because they are affected by pressure drops. Volumetric flow meters should not be compared to mass flow meters. Mass flow meters can be compared against one another provided there are no leaks between the two meters and they are set to the same standard temperature and pressure. Both meters must also be calibrated (or set) for the gas being measured. M Series mass flow meters are normally set to Standard Temperature and Pressure conditions of 25° C and 14.695 PSIA. The standard temperature and pressure can be changed via the front panel and serial communications. It can also be ordered with specialty standard temperature and pressure.
- My volumetric meter reading is strange, inconsistent, or incorrect.
Make sure you use a volumetric flow meter only under low pressure (close to atmospheric) and with little to no back pressure for accurate readings. Mass meters should be used for higher pressure applications.
- The device jumps to zero at low flow.
Mass flow and pressure devices feature a programmable deadband or zero band. The factory setting is usually 0.5% of full scale. This can be adjusted via the front panel or serial communications.
Gas Compatibility Concerns
- The display does not come on or is weak.
Check power and ground connections.
- The output signal is lower than the reading at the display.
This can occur if the output signal is measured some distance from the meter as voltage drops in the wires increase with distance. Using heavier gauge wires, especially in the ground wire, can reduce this effect.
- The device is responding slower than expected.
Mass flow devices feature a programmable geometric running average (GRA) for both pressure and flow rate measurements that may lead to a slower perceived response time. This can be adjusted via the front panel or serial communications. Controllers also have programmable valve tuning available via the front panel and serial communications which can further improve the response time.
- My device is locked and 'LCK' is showing on the screen
Alicat devices come with a locking option for applications in which the buttons may accidentally be pressed changing crucial device settings. Devices with newer firmware revisions can be unlocked by pressing and holding the outer four buttons on the front panel. All devices can be unlocked via serial communications. Please follow the steps below.
- Download Serial Terminal from www.alicat.com/support/software-drivers.
- Make sure all drivers associated with the cables are installed. Please look for any discs that came with the cables.
- Open the “Control Panel” and then open “Device Manager”.
- Under “Ports”, find the COM number the Alicat is connected to and write this down for later.
- Open Serial Terminal
- Serial Terminal will ask for the COM port and baud rate. Enter the COM port you found in part 2 and a baud rate of 19200.
- Type A$$U and press enter.
- Your device should now be unlocked!
Occasionally the device unit ID may be different than A. If A$$U does not unlock, try B$$U or C$$U, etc all the way to Z$$U. To change the unit ID back to A, you can type *@=A and press enter to give all connected devices a unit ID of A.
- The RS-232 Serial Communications is not responding.
Check that your unit is powered and connected properly. Be sure that the port on the computer to which the unit is connected is active. Confirm that the port settings are correct per the RS-232 instructions in this manual. When connecting multiple devices to a single COM port, please ensure that all devices have a unique unit ID.
- The BB9 multi-drop box isn't showing up under COM ports in my device manager.
- If the BB9 multi-drop box is showing up under “other” in your device manager instead of “Ports (COM & LPT)”, the most likely cause is missing drivers. While these should install automatically when plugging into your computer, occasionally security settings can prohibit them from installing. Please try installing the drivers directly from www.alicat.com/drivers.
- If using a USB port with Windows 7 and an error pops up saying “One of the USB devices attached to this computer has malfunctioned and Windows does not recognize it”, the USB port itself is having issues. Microsoft has released a solution on one of their forums at www.answers.microsoft.com/en-us/windows/forum/windows_7-hardware/one-of-the-usb-devices-attached-to-your-computer/b8a2fc66-5e58-48a3-9d3b-1db2858c3a9e.
- If using the 9 pin serial connection on your computer and nothing shows up in device manager, it’s possible the COM port on the computer has died. BB9 multi-drop boxes come with cables to connect to 9 pin serial ports or USB ports. Please try connecting to the computer using a different port and checking the device manager again.