Here are the instrument troubleshooting questions most frequently posed to our service department, along with answers that, in some cases, must be generic. Refer also to our Knowledge Base.
Please feel free to address any of your concerns—from instrument problems and applications questions, to parts availability and pricing—to our service department.
Click on any instrument troubleshooting question below to view the answer.
▶ Blank display and/or unable to zero the unit [on 4000 Series analog and digital portable analyzers]
Check/replace AA or C size alkaline batteries. Make sure that Nickel-Cadmium batteries are fully charged. Allow sufficient time for re-stabilization after battery replacement or charging.
Every three months at a minimum. Monthly calibration is recommended, especially for lower range/more critical applications.
Our ECS (Electronic Calibration Service) is offered for those customers who find it inconvenient to obtain their own calibration standard.
▶ What is considered “normal” sensor weight loss? [Applicable to LD, RM, and PLC Series continuous monitoring systems, and portable sensors for formaldehyde and hydrazine]
A weight loss of more than 50 grams makes sensor restoration difficult, and beyond 100 grams, it is virtually impossible. Weight loss is affected by ambient humidity, flow rate, and in certain cases, the type of sensor being used.
The sensors work best, and last longer, if they are kept moist. If your sensor is losing more than 50 grams of water per month, add water every two weeks.
▶ Where can I find information on other gases that might interfere (i.e. affect the reading either positively or negatively) with my measurement?
▶ Can you explain the mysterious “2:00 AM false alarms” occurring on my ethylene oxide monitoring system?
Your EtO monitoring system is very sensitive, and must respond to sub parts-per-million (ppm) concentrations of this gas. It may be that maintenance crews are using floor wax, strippers, assorted cleaning products, or isopropyl alcohol, and these compounds can cause a response on the system, especially since they would be present at concentrations in excess of 500 ppm.
The sampling pump(s) of the system should be shut down temporarily during these maintenance operations, to avoid false alarms. A special timer, that re-starts the sampling pump(s) after a customer-adjustable time interval, is available to perform this action automatically.
Do not attempt to remove these interferences by covering the sample inlet with a rag or other obstruction, as this can clog up the sample inlet, thus causing the pump to pull its full vacuum on the sensor—leading to irreversible sensor damage.
Typical sensor life is 2-3 years. This assumes proper maintenance, and infrequent exposure to concentrations well above the intended measuring range of the instrument.
This scrubber material comes in purple pellets, that will turn dark brown or black with use. The scrubber should be replaced when the majority of the pellets in the tube have turned color.
Dispose of an old sensor the same way you would dispose of an old car battery. Facilities exist in most communities to handle this type of waste.
▶ Do I need a return material authorization (RMA) number to send equipment back to Interscan for service?
Yes. We do this to serve you better and more efficiently. Please request an RMA form here .
Most orders for sensors and parts can be shipped within two days. If you have a super-rush situation, please notify us! An expedite fee will apply to specially expedited/rush orders.
These can manifest as follows:
a) Sudden or erratic changes in meter display (or data logging/recording device), lasting a few seconds or less
b) Erratic changes in meter display (or data logging/recording device) which repeat at fixed intervals at certain times of day
c) Over-range or under-range indicated on meter (or data logging/recording device) lasting for long periods. [Excluding when sensor is first installed or batteries changed.]
Electrochemical and purely electronic devices can both fall victim to RFI. Fortunately, precautions can be taken to minimize RFI. It is prudent to make yourself aware of RFI sources within the monitoring environment.
Machinery with large motors or welders can produce RFI signals. Light sources such as large neon and fluorescent can be a source of RFI. Service crews could be using communications devices (two-way radios) which use RF. Monitoring at times when communications devices are being used, and comparing readings at periods of non use can determine if RFI truly is an issue.
Grounding is a means to minimize RFI. Fixed monitors should be checked to make sure the round ground lead has not been damaged or removed at the AC wall plug. Direct wiring must have a ground lead (usually green). Portable monitors can have the metal case connected to an earth ground or cold water pipe within the area. Note that grounding wire should be kept to a minimum length. Long grounding wires can have the reverse action and act as antennas.
Different enclosures provide varying degrees of protection dependent on proper grounding. Fiberglass based enclosures allow the highest response to RFI. Conductive coated fiberglass protects against weak signals. Aluminum is better than fiberglass.
Note that Interscan uses a particular aluminum alloy in its portable analyzers with low levels of magnesium, to minimize sparking when used in hazardous areas (thus enhancing the intrinsic safety). Steel is the best defense against RFI. It has drawbacks in that the weight is prohibitive for use with portable monitors, and the cost is greater.
Connecting external devices such as recorders or PLCs must have the leads shielded on one end only with the shield connected to a proper ground source. Shortest ground leads are best.
Specialized RFI-shielded enclosures are available. As such, planning is also crucial to minimize RFI. These matters should be discussed with our application engineers.
These can manifest as follows:
a) Drop in flow rate, as observed on panel rotameter or digital flow indicator [RM Series, LD Series, and multipoint systems].
b) Loss in instrument sensitivity
c) Drop in flow rate and loss in instrument sensitivity, as these are related
Sensor clogs or partial occlusions generally derive from two sources.
In the first case, too much distilled or deionized water is being added to refillable sensors. Alternatively, the water is not being added properly. This can cause small amounts of electrolyte to pass through the semi-permeable membrane of the sensing electrode, which dries and leaves a residue behind. The residue can accumulate over time and decrease or prevent flow of gas through the sensor.
The second source is particulate contamination. All continuous monitoring systems [RM Series, LD Series, and multipoint systems] are provided with sample inlet filters. Portable analyzers (4000 Series) can also be provided with a filter-equipped sampling probe, and this should be done in any application that will require monitoring in dusty areas. Contact the service department for further details.
ECS works as follows:
The ECS certification details zero and span adjustments that are to be made on the instrument, to set it up with the newly-obtained certified sensor. These adjustments do not require any calibration gas, and use only a simple digital voltmeter.
As indicated on the certification sheet, the ECS program verifies sensor sensitivity and calibration status only. It does not certify the instrument as a whole. Most importantly, the ECS program is not a substitute for basic instrument maintenance, nor does it check for malfunction of the instrument components.
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