Frequently Asked Questions

Valve Communication and Control

Find answers to your questions about Stonel brand Valve Communication and Control products and Process Networking solutions.

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Since these are solid state sensors, you will not be able to bench test them by measuring continuity. Solid state sensors need power to operate. Here is a diagram that shows the test circuit. The IMO for the product contains the complete test procedure.

I am replacing a contact type switch unit with a Stonel model that has SST solid state sensors, how do the sensors get wired into my control system?

2-wire solid state sensors electrically act like a SPST contact type switch. You would connect the wire that was connected to the common of the contact switch to the Common (C) terminal of the SST sensor and the wire from the NO contact of the switch to the NO terminal of the SST sensor. Here is a diagram that shows the basic circuit. As with a contact type switch, no additional power is required other than what is provided by the control system input card.

Yes, we sell rebuild kits and they are easy to install. See the available kits on the “downloads” tab for each of the Stonel Axiom platform pages. 

AN/ANX series

AX series

AMI series (discontinued product)

Stonel does offer mechanical DPDT switches. However for applications that are not appropriate for mechanical switches or applications where reliability and long cycle life are important, we would recommend using 4x SPDT switches. The SPDT Reed-Type proximity switches have much longer cycle life and reliability than mechanical switches, and 4x SPDT has the same contacts as 2x DPDT.

Stonel has many options for these applications. If your application calls for a solenoid valve as well, consider the Axiom model, AN45. Other options exist in the Eclipse, Quartz and Prism platforms. See the model selection guides for each platform for applicable options. Here is a diagram showing typical intrinsically safe wiring schematics.

IS specs for solenoids are commonly expressed in terms of the voltage that is applied to the safe area side of the barrier (non-hazardous area). In fact the barriers have inherent resistance and that in conjunction with the coil resistance give you a voltage drop across the barrier. This is usually about half of what the voltage is that is applied to the non-classified side of the barrier (if barrier end-to-end resistance and coil resistance are equal).

You may have noted that solenoid coil manufacturers state for their intrinsic safety coils that if used without a barrier a series resistor of a certain value must be used, this is to provide the proper voltage drop, and in most cases, is a 12 volt drop from the 24vdc, with only 12vdc being applied to the coil.

Stonel intrinsic safety coils in AMI44 and PM44 require the use of a 24vdc barrier with an end-to-end resistance of 250-305 ohms. This provides the 12vdc required by our coils.

For most cases, the newest option, the QXT/QNT high performance digital position transmitter is the best choice.  It features a non contact mag res sensor and combines high precision feedback with easy set-up and configuration via push buttons. This one is designed to be very robust and able to perform well  in very harsh environments, like high vibration or wet / humid applications.   

The QX5/QN5 features a potentiometer based 4-20mA position transmitter. It is sufficient for most applications where high precision is not needed and the device is not exposed to high vibration. In high vibration or high cycle applications standard potentiometers will typically function, but may have a shortened life. This is caused by the wiper wearing a groove in the resistive element. This will cause the reading to jump as it climbs over the edge of the groove.

QX7/QN7 is also potentiometer based, but utilizes a high performance, precision, MIL-spec potentiometer. It features a hardened co-molded resistance element and precision stainless steel ball bearings. This version provides precise, reliable feedback and withstands high cycle and high vibration applications.

So if you need precise feedback or have high vibration application select either of the high performance options, otherwise the standard version should perform well in most other applications.  One more comment, If SIL Certificate is needed for your 4-20mA position transmitter, then your options are limited to Q_5, and Q_7.

Only one device can be placed on a Protected “T” or Protected Drop switch due to the fact that the current draw of two devices would be higher than the reset current level of the Protected “T” or Protected Drop switch (less than .025 Amps).

Yes, you can operate more than one ASi Network with one ASi power supply by using power conditioners. You will need 1 power conditioner per network or segment. This is required for signal decoupling between the two networks. Standard power supply and power conditioner current limits apply.

The only method available for redundant power supplies on an AS-i Network is through the use of a Power conditioner for redundant inputs. When using this power conditioner, two supplies are wired in “hot-redundant” mode to the power conditioner terminal block. The AS-i connection is made from the output of the Power conditioner to the network to be powered.

All devices indicating a fault could be explained by ‘no communication’ over the ASi wire. The following cases are possible explanations for such a scenario: (1) A non ASi power supply is used to power the system (2) A non ASi device has been wired to the ASi cable (3) Faulty ASi power supply (4) Faulty ASi master or gateway.

Many factory automation plants use the AS-i flat cable. However in the process industries, round cable is almost always used. When using round cable, it is recommended you use 2 conductor, 16AWG, non-twisted, non-shielded wire with the following electrical specifications (at 167 kHz): Capacitance 52 – 78 pF per meter, Impedance 64 – 96 Ohm per meter and Conductance 4 – 5 nS per meter. See our AS-i cable here

No, there is too much capacitance inherent in the AS-i devices (enables communication) However, AS-i I/O modules could be located in the safe area and I.S. Sensors could be run through a barrier to the I/O Module.

Here is how to determine if a barrier is capable of operating our IS Solenoid. If all of the following are true, our solenoid will work with the barrier in question.

General Requirements:
1. Ui (aka Vmax) must be greater than or equal to Uo (aka Voc) (Ui >= Uo)
2. Ii (aka Imax) must be greater than or equal to Io (aka Isc) (Ii >= Io)
3. Pi must be greater than or equal to Po (Pi >= Po)
4. Ci + Ccable must be less than Co (aka Ca) (Ci+Ccable<Co)
5. Li + Lcable must be less than Lo (aka La) (Li+Lcable<Lo)

For AN45, ANX45 and PI45:
6. Barrier must be capable of handling 45 mA draw or more.
7. Internal resistance of Barrier must be 400 ohms or less.
8. Nominal output voltage without load (0 mA) must be 18 VDC to 28 VDC.

For AMI44, AX44 and PM44:
6. Barrier must be capable of handling 50 mA draw.
7. Internal resistance of 24 VDC Barrier must be 250 to 305 ohms.

Yes - FM Approvals has been accredited by the Standards Council of Canada (SCC) as a testing and certification organization for electrical and electronic equipment.

All devices indicating a fault could be explained by ‘no communication’ over the ASi wire. The following cases are possible explanations for such a scenario: (1) A non ASi power supply is used to power the system (2) A non ASi device has been wired to the ASi cable (3) Faulty ASi power supply (4) Faulty ASi master or gateway.

Check the product mapping document to assist you with selecting the appropriate Stonel product series for your industry application.