This is the first time I work with TEDS data and I hope that someone can help me.
I try to read out the TEDS data of the following microphone:
G.R.A.S 40AE 1/2" microphone together with the G.R.A.S 26CF 1/2" CCP preamp.
The GRAS product catalogue says: "46AE is a 1/2" free-field general purpose high sensitivity microphone set with built-in TEDS and BNC connector."
I am using a NI PXIe-6363 DAQ card (and also tried a PXI-6259 DAQ card with the same result). Following the supported properties, both should be able to read the TEDS data:
I could not get it working in LabVIEW and hence tried to get the TEDS data in MAX first. However I can not choose the "Scan for HW TEDS" button in MAX, see pic below.
What do I have to set or install that I can scan for HW TEDS and how can I read the TEDS data?
i have two ideas
1. use a card which can directly read out the EEPROM from the TEDS sensor like the PXI-4462
2. there is the SC-2350 box which can also be used for TEDS and the DAQ cards
What i did not find is, if the G.R.A.S microphone has the additional wires or how to connect them to the SC-2350.
Your device is a CCP (constant current preamp?) ?
Found it at GRAS
CCP stands for “Constant Current Power” and describesG.R.A.S. power supplies that maintain a constant level ofcurrent for driving IEPE transducers like this preamplifier which can be used with prepolarized microphone cartridges....
The input bias current of your DAQs of about 100pA doesn't match the 4mA minimum current specified 😄
So your DAQ needs to support IEPE supply and TEDS. A simple external IEPE supply wouldn't work with TEDS since the TEDS for IEPE devices need to reverse the current during readout. (AFAIK)
A lot of NI DAQs that support IEPE only have 2mA drive current, GRAS specified 4mA !
So ask GRAS if it will work with 2mA or look for a IEPE DAQ device that has at least 4mA current drive capabilities.
Since they need power to generate the HV for the condenser mic, you migth be unlucky...
BTW I wonder about the <50 Ohm output impedance specification of GRAS. Ohms law tell me 14V/20mA = 700 Ohm minimum 😄